Inks comprising modified pigments and methods for making and using the same

ABSTRACT

An ink composition that includes a self-dispersing pigment that has about 0.02 to about 1.0 mMoles of S and about 0.2 to about 2.0 mMoles of active hydrogen per gram of pigment, water, and an organic solvent. A method of making an ink composition that includes sulfonating a pigment, subsequently oxidizing the pigment to produce a modified pigment, and incorporating the modified pigment into an ink.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119(e) to U.S.Provisional Patent Application No. 60/855,573 filed Oct. 31, 2006, theentire content of which is hereby incorporated by reference.

FIELD OF USE

The present invention relates to a method of making self-dispersingpigments. More particularly, the present invention relates to thesurface modification of pigments, as well as inks, such as inkjet inks,comprising surface-modified pigments.

BACKGROUND

Pigments offer several advantages over water-soluble dyes when it comesto inkjet inks. Pigments may exhibit at least one of greater lightresistance, water resistance, optical density and edge acuity thanwater-soluble dyes. Unfortunately, pigments also have a greaterpropensity to settle during storage, thus initially limiting their usein inkjet inks. The advent of media mills to grind pigment particles tosub-micron level combined with chemical additives for colloidalstability has propelled the use of pigment dispersions in inkjet inkformulations. However, chemical additives can increase the viscosity ofa dispersion such that it becomes difficult to jet the ink from thesmall orifices in an inkjet printhead. Moreover, chemical additives canadd significant cost to the preparation of inkjet inks and are thereforeeconomically unfavorable as well. A need remains for improved inkcompositions, especially for use in inkjet printers, which overcome theproblems typically associated with current dye-based systems and pigmentsystems employing chemical additives.

SUMMARY

In one embodiment, the invention provides an ink composition thatincludes a self-dispersing pigment that has about 0.02 to about 1.0mMoles of S and about 0.2 to about 2.0 mMoles of active hydrogen pergram of pigment, water, and an organic solvent.

In another embodiment, the invention provides a method of making an inkcomposition that includes sulfonating a pigment, subsequently oxidizingthe pigment to produce a modified pigment, and incorporating themodified pigment into an ink.

Other aspects of the invention will become apparent by consideration ofthe detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 displays low resolution X-Ray Photoelectron Spectroscopy (XPS)spectra for carbon black (Sample 1), carboxy modified carbon black(Sample 2), sulfonated carbon black (Sample 3) and sulfonated, carboxymodified carbon black (Sample 4), as set forth in Example 20.

FIG. 2 displays high resolution XPS C 1s spectra for the samples in FIG.1.

FIG. 3 displays high resolution XPS O 1s spectra for the samples in FIG.1.

FIG. 4 displays high resolution XPS S 2p spectra for the samples in FIG.1.

FIG. 5 displays Scanning Electron Microscopy (SEM) images (15.0 kV×500 K60 nm) of (a) carbon black having an average particle diameter of˜39.3±3 nm, (b) carboxy modified carbon black having an average particlediameter of ˜31.1±3 nm, and (c) sulfonated, carboxy modified carbonblack having an average particle diameter of ˜38.7±2 nm, where each hasbeen dried at room temperature, as set forth in Example 21.

FIG. 6 is a graph of Temperature in ° C. (x-axis) versus Weight %(y-axis) obtained by Thermal Gravimetric Analysis (TGA) for carbonblack, carboxy modified carbon black and sulfonated, carboxy modifiedcarbon black, as set forth in Example 22.

FIG. 7 is a graph of Temperature in ° C. (x-axis) versus Weight %(y-axis, left) and Differential Temperature/Differential Weight (y-axis,right) obtained by TGA for sulfonated, carboxy modified carbon black, asset forth in Example 22.

FIG. 8 is a graph of Temperature in ° C. (x-axis) versus Weight %(y-axis, left) and Differential Temperature/Differential Weight (y-axis,right) obtained by TGA for carboxy modified carbon black, as set forthin Example 22.

FIG. 9 is a graph of Temperature in ° C. (x-axis) versus Weight %(y-axis, left) and Differential Temperature/Differential Weight (y-axis,right) obtained by TGA for carbon black.

DETAILED DESCRIPTION

Before any embodiments of the invention are explained in detail, it isto be understood that the invention is not limited in its application tothe details of construction and the arrangement of components set forthin the following description. The invention is capable of otherembodiments and of being practiced or of being carried out in variousways. Also, it is to be understood that the phraseology and terminologyused herein is for the purpose of description and should not be regardedas limiting. The use of “including,” “comprising,” or “having” andvariations thereof herein is meant to encompass the items listedthereafter and equivalents thereof as well as additional items.

It also is understood that any numerical range recited herein includesall values from the lower value to the upper value. For example, if aconcentration range is stated as 1% to 50%, it is intended that valuessuch as 2% to 40%, 10% to 30%, or 1% to 3%, etc., are expresslyenumerated in this specification. These are only examples of what isspecifically intended, and all possible combinations of numerical valuesbetween and including the lowest value and the highest value enumeratedare to be considered to be expressly stated in this application.

Surface Modified Pigments

One aspect of the present invention relates to a method for makingstable, self-dispersing pigments.

As used herein, the term “pigment” means a colored material insoluble ina solvent medium used to impart color to a substrate such as plain orcoated paper, film and other types of receiving media.

As used herein, the term “self-dispersing pigment” means a pigmenthaving stabilizing groups covalently attached to its surface such thatthe pigment forms a stable aqueous dispersion in the absence of anyadditional dispersing agents.

As used herein, the term “stable” means that on aging the dispersionwill undergo minimal changes as demonstrated by less than 10% change inmeasured critical properties such as mean particle size, large particlecount, viscosity, surface tension or pH, when the dispersion is storedat ambient temperature for at least about 3 months, at least about 6months, or at least about 2 years, or when the dispersion is stored at70° C. for at least about 1 week, at least about 2 weeks, at least about3 weeks or at least about 4 weeks.

The method for making the self-dispersed pigments generally comprises(1) attaching hydrophilic groups to the surface of the pigment bysulfonation and (2) subsequently oxidizing the surface of the pigment toimpart greater charge density around the particle. The oxidation stepadds surface modifying groups that may include carboxyl groups, lactonegroups, phenolic groups, quinone groups and combinations thereof. Moreparticularly, the oxidation step adds surface modifying groupscomprising carboxyl groups.

Pigments

Pigments that may be surface modified according to the present inventionmay include, but are not limited to, azo pigment, phthalocyaninepigment, anthraquinone pigment, quinacridone pigment, thioindigopigment, triphenylmethane lake pigment, and oxazine lake pigment.Specifically, those having yellow colors include, for example, C. I.Pigment Yellow 1, 2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 65,74, 83, 97, 138 and 155. Those having red colors include, for example,C. I. Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16,17, 18, 19, 21, 22, 23, 30, 31, 32, 37, 38, 39, 40, 49, 50, 51, 52, 53,55, 60, 64, 83, 87, 88, 89, 90, 112, 114, 122, 123 and 163. Those havingblue colors include, for example, Solvent Blue 67 and C. I. Pigment Blue2, 3, 15, 16, 22 and 25. Those having black colors include, for example,C. I. Pigment Black 1 and 7. Commercially available colored pigmentsinclude, for example, Pigment Red 122 (available from Lansco Colors,Montvale, N.J.), Pigment Red 122 (available from BASF Color, Charlotte,N.C.), Pigment Red 122 (available from Clariant Colors, Charlotte,N.C.), Pigment Red 122 (available from Sun Chemical, Cincinnati, Ohio),Pigment Blue 15:1 (available from Fanwood Chemical, Fanwood, N.J.),Pigment Blue 15:3 (available from BASF Corporation, Charlotte, N.C.) andSolvent Yellow 33 (available from Rainbow Chemicals, Northbrook, Ill.).

Suitable pigments also include carbon black. Carbon black is the genericname for carbon particles derived from the thermal decomposition or theincomplete combustion of natural gas and hydrocarbons, such as aromaticoils on coal tar basis, mineral oils, coal tar distillate, andacetylene. More than 100 individual grades of carbon black are availableon the market today, each with its own distinctive set ofcharacteristics and properties. Any acidic carbon black, neutral carbonblack and alkaline carbon black may be beneficially subjected to thetreatment disclosed in the present invention. This includes channelblacks, gas blacks, lamp blacks, thermal blacks, acetylene blacks andfurnace blacks. More particularly, suitable carbon blacks includechannel blacks. The quality of carbon black utilized will have an impacton the critical properties of the dispersion such as mean particle size,opacity, color shade, stability, etc. Examples of commercially availablecarbon blacks include, but are not limited to, those available fromCabot (Elftex 8, Black Pearls® 490, Black Pearls® 120, Monarch® 120,Monarch® 700, Monarch® 880, Monarch® 1000, Monarch® 1100, Monarch® 1300,Monarch® 1400, Mogul® L, Regal® 99R, Regal® 250R, Regal® 300R, Regal®330R, Regal® 400R, Regal® 500R, Regal® 660R), Degussa (NIPex® 150 IQ,NIPex® 150, Printex® 55, Printex® 80, Printex® 90, Printex® A, Printex®G, Printex® U, Printex® V, Printex® 140U, Printex® 140V, Purex® LS 35,Corax® HP 160, Thermal Black N 990, NIPex® 160 IQ, NIPex® 90, Specialblack 4, Special black 4A, Special black 5, Special black 6, Specialblack 100, Special black 250, Color black FW1, Color black FW2, Colorblack FW2V, Color black FW18, Color black FW200, Color black S150, Colorblack S160 and Color black S170), Columbian (Raven® 780, Raven® 5000UII, Raven® 1255, Raven® 2500 U, Raven® 3600 U, Raven® 3500, Raven®7000, Raven® 1220 and Raven® 1225) and Mitsubishi Kagaku K.K. (MA8,MA11, MA77, MA100, MA220, MA230, MA600, MCF88, #10B, #20B, #30, #33,#40, #44, #45, #45L, #50, #55, #95, #260, #900, 970#, #1000, #2200B,#2300, #2350, #2400B, #2650, #2700, #4000B and CF9).

Carbon black is available in a variety of particle sizes. Generally,smaller particle sizes are associated with larger surface areas, andlarger surface areas can accommodate a higher concentration ofhydrophilic surface groups, which ultimately enhance the dispersibilityof the carbon black in aqueous-based media. Therefore, particle size caninfluence the dispersibility of a surface-modified pigment. The averageprimary particle size of carbon blacks in the present invention may beless than about 30 nm, particularly less than about 20 nm, and moreparticularly less than about 10 nm. Aggregates of carbon black particlesmay be less than about 200 nm, particularly less than about 150 nm, andmore particularly less than about 100 nm. The surface area of carbonblack particles may be greater than about 100 m²/g, particularly greaterthan about 150 m²/g, and more particularly greater than about 200 m²/g.Carbon black particles with larger dimensions may be comminuted to adesired size either before or during surface modification using anynumber of techniques known to those skilled in the art. Such techniquesmay include, but are not limited to, a ball mill, an attritor, a flowjet mixer, an impeller mill, a colloidal mill and a sand mill (e.g., onecommercially sold under the tradename ‘Super Mill’, ‘Agitator Mill’,‘Dyno-mill’ or ‘Beads Mill’). Mill media may include, but are notlimited to, glass beads, zirconia beads and stainless steel beads. Millmedia may comprise particles ranging in size from about 0.01 mm to about5 mm, and more particularly from about 0.1 mm to about 0.3 mm. If thecarbon black is easily crumbled, a rotary homogenizer or an ultrasonichomogenizer may be used to reduce particle size. In one embodiment, asurface-modified black pigment is made from a commercial grade carbonblack pigment consisting of primary particle sizes less than about 30 nmand aggregates not more than about 200 nm with a surface area greaterthan about 100 m²/g.

By way of example, surface modification of carbon black will begenerally described below. However, the surface modification may besimilarly applied to other colored pigments, such as those mentionedabove and described in the Example section below.

Sulfonation

Hydrophilic groups comprising sulfonic acid are attached to carbon blackby sulfonation with sulfuric acid, oleum (fuming sulfuric acid) or acombination thereof. Attachment of sulfonic acid groups directly on thesurface of the carbon black pigment may also be achieved by sulfonatingwith other known chemical agents such as chlorosulfonic acid or bydisplacement of a leaving group attached to the pigment, such as halogenwith a suitable reagent such as sodium bisulfite.

In the case of sulfonating carbon black with sulfuric acid, oleum or acombination thereof, a suitable acid strength for sulfonation lies inthe range of about 85% to about 104% (weight of sulfuric acid/totalweight), particularly in the range of about 90% to about 102% (weight ofsulfuric acid/total weight), and more particularly in the range of about99% to about 101% (weight of sulfuric acid/total weight). Thecombination of acid strength, reaction temperature and durationdetermine how many sulfonic acid groups are attached to the surface ofthe pigment, therefore strength of sulfuric acid used in the presentinvention is best determined in conjunction with other criticalparameters. In one embodiment, as represented by Example 2, sulfonationis carried out with a mixture of carbon black and equal amounts ofconcentrated sulfuric acid and oleum (20% excess SO₃). In otherembodiments, as represented by Example 1, sulfonation is carried outwith a mixture of carbon black and 20% oleum. In yet other embodiments,as represented by Example 3, sulfonation is carried out with a mixtureof carbon black and 99.4% sulfuric acid. Similar acid strengths may beemployed in the sulfonation of pigments other than carbon black. In oneembodiment, as represented by Example 12, sulfonation is carried outwith a mixture of C.I. Pigment Red 122 and 90% sulfuric acid.

The ratio (by weight) of carbon black to acid is largely determined as afunction of operational efficiency which includes mixing, ease oftransfer and cost. A minimum of acid to carbon ratio of about 4:1(wt/wt) is needed to get good mixing throughout the reaction. A largeexcess such as a ratio of about 20:1 (wt/wt) does not result insignificant benefit but increases the cost of both materials and wastehandling.

Sulfonation of the carbon black is carried out at elevated temperaturesfor a period of up to about 2 days. The reaction temperature duringsulfonation may be at least about 25° C., particularly at least about80° C., and more particularly at least about 120° C. Furthermore, thereaction temperature during sulfonation may be less than or equal toabout 160° C., particularly less than or equal to about 140° C., andmore particularly less than or equal to about 120° C. This includesembodiments where the reaction temperature during sulfonation is about80° C. to about 120° C. Generally, higher temperatures require shorterreaction times to achieve a desirable concentration of sulfonic acidgroups on the surface of carbon black. For example, the desiredsulfonation at a reaction temperature of 140° C. may take about twohours, whereas the same degree of sulfonation at 80° C. would beexpected to take more than two hours. In some embodiments, a suitablereaction time may be at least about 12 hours, in others at least about24 hours, and in yet others at least about 40 hours. In otherembodiments, the suitable reaction time may be less than or equal toabout 48 hours, in others less than or equal to about 30 hours, and inyet others less than or equal to about 20 hours. This includesembodiments where the suitable reaction time is from about 2 hours toabout 48 hours. The contents of the reaction vessel are stirred duringsulfonation to insure adequate mixing.

After sulfonation, the reaction mixture may be quenched in water. Insome embodiments, the reaction mixture may be cooled to a temperatureless than about 100° C. prior to quenching, in others to a temperatureof less than about 80° C. prior to quenching, and in yet others to atemperature less than about 60° C. prior to quenching. This includesembodiments where the reaction mixture is cooled to a temperature ofabout 60° to about 65° C. prior to quenching. The water into which thereaction mixture is added may be at or below a temperature of about 10°C. using, for example, ice, a cooling device or combination thereof. Thesulfonated product, referred to as a carbon sulfonation cake, may beisolated from the water by filtration and washed free of excessreactants and water soluble products.

Oxidation

The carbon sulfonation cake is subsequently oxidized with oxidizingagents known to modify the carbon surface by attaching hydrophilicgroups such as carboxyl groups, lactone groups, phenolic groups, quinonegroups and combinations thereof. The oxidation method may include, butis not limited to, contact with air, a gas phase oxidation method usingreaction with a nitrogen oxide or ozone, a liquid phase oxidation methodusing an oxidizing agent such as nitric acid, potassium permanganate,potassium dichromate, perchloric acid, a hypohalite, hydrogen peroxide,a bromine aqueous solution or an ozone aqueous solution. In oneembodiment, oxidation of the carbon black is carried out using ahypohalogenous acid and/or its salt. Suitable hypohalogenous acids orsalts thereof include, but are not limited to, sodium hypochlorite(NaOCl), potassium hypochlorite (KOCl), sodium hypobromite (NaOBr), andpotassium hypobromite (KOBr). More particularly, the oxidizing agentcomprises NaOCl.

In some embodiments, oxidation of the carbon sulfonation cake includesreacting carbon black with hypohalite salts in an aqueous medium. Thecarbon sulfonation cake may be dispersed in deionized water prior to theaddition of hypohalite salts. The initial concentration (by weight) ofhypohalite salt in the reaction mixture is at least about 1%,particularly at least about 5%, and more particularly at least about10%. Furthermore, the concentration of hypohalite salt may be less thanor equal to about 14%, particularly less than or equal to about 12% orabout 10%, and more particularly less than or equal to about 7% or about5%. This includes embodiments where the concentration of hypohalite saltis about 5% to about 10%. The proportion (by weight) of hypohalite saltto carbon sulfonation cake is about 1:20 to about 1:5, particularlyabout 1:15 to about 1:8, and more particularly about 1:11 to about 1:9.For pigments other than carbon black, the proportion (by weight) ofhypohalite salt to sulfonation cake is about 1:5 to about 1:1.

Reaction between the carbon sulfonation cake and oxidizing agent mayoccur for a period of about 1 to about 2 hours with mixing. Ifnecessary, to consume all of the hypochlorite, the oxidation reactioncan be carried out at an elevated temperature of about 30° C. to about90° C. In some embodiments, the reaction may be carried out at about 80°C. In other embodiments, the reaction may be carried out at about 60° C.The oxidation step may, but need not, be repeated one or more times.

Oxidation of the carbon black creates acidic surface groups that canlower the pH of the reaction mixture. A decrease in pH may result in adestabilization of the modified pigment dispersion during the oxidationtreatment and may also result in an increase in viscosity. Therefore,the pH may be adjusted, as needed, before and during oxidation with abasic reagent. The pH of the reaction mixture prior to oxidation may begreater than or equal to about 7, particularly greater than or equal toabout 10 or about 11, and more particularly greater than or equal toabout 12. The pH of the reaction mixture during oxidation may be greaterthan or equal to about 9, particularly greater than or equal to about10, and more particularly greater than or equal to about 11. The pH maybe adjusted by any known method in the art including, for example, theaddition of base. Suitable bases may include, but are not limited to,alkali hydroxides and calcium free alkali hydroxides (e.g., NaOH, KOHand LiOH), alkali carbonates and bicarbonates (e.g., NaHCO₃, KHCO₃), andorganic bases (e.g., dimethylethanol amine and triethanol amine). Inparticular, a suitable pH adjuster comprises calcium free sodiumhydroxide.

Isolation of Surface Modified Pigment

After oxidation, the modified pigment, such as the modified carbon blackdescribed above, may be isolated from the reaction mixture as a drypowder. The resultant modified pigment may be purified by using anynumber of techniques known to those skilled in the art to removeunreacted raw materials, byproduct salts and other reaction impurities.Purification techniques may include, but are not limited to, filtration,centrifugation, or a combination of the two. The modified pigment mayalso be isolated, for example, by evaporation or it may be recovered byfiltration and drying using techniques known to those skilled in theart.

Alternatively, the modified pigment may be delivered as a concentratedaqueous pigment dispersion. Dispersions of the pigments of the presentinvention may be purified to remove impurities and other undesirablefree species which can co-exist in the dispersion as a result of themanufacturing process. Purification techniques may include, but are notlimited to, water washing, reverse osmosis, and ultrafiltration. In someembodiments, dissolved impurities may be removed by ultrafiltrationuntil each of the chloride content and the sulfate content of the feedsample adjusted to 10% solids is less than about 150 ppm, particularlyless than about 100 ppm, and more particularly less than about 10 ppm.If necessary, the pH of the dispersion may be adjusted prior topurification. A sufficient amount of acid or base may be added to adjustthe pH of the dispersion to at least about 7, particularly to at leastabout 8, and more particularly to at least about 9. This includesembodiments where the pH of the dispersion is about 7 to about 9. Thedispersion may be concentrated if desired by removal of some of thewater. In some embodiments, the dispersion is concentrated to at leastabout 8% or about 10% solids, in others to at least about 18% solids,and in yet others to at least about 20% solids. This includesembodiments where the dispersion is concentrated to about 14% to about16% solids.

A biocide may also be added to the dispersion to inhibit the growth ofmicroorganisms. Examples of suitable biocides include, but are notlimited to, sodium benzoate, pentachlorophenol sodium,2-pyridinethiol-1-oxide sodium, sodium sorbate, sodium dehydroacetate,benzisothiazolinone, 1,2-dibenzothiazolin-3-one, methylisothiazolinoneand chloromethylisothiazolinone. Commercially available biocides includeProxel® CRL, Proxel® BDN, Proxel®5 GXL, Proxel® XL-2, and Proxel® TN(available from Arch Chemicals, Smyrna, Ga.).

The dispersion may be filtered through filter cartridges as required forthe designated end use of the dispersion. In some embodiments, thenominal pore size of the filter cartridge is less than or equal to about5 microns, particularly less than or equal to about 1 micron, and moreparticularly less than or equal to about 0.5 or about 0.3 micron.

In addition to powders and dispersions, the modified pigment may also beisolated as a water wet presscake. In presscake form, the modifiedpigment is not agglomerated to the extent that it is in dry form andthus the modified pigment does not require as much deagglomeration whenused, for example, in the preparation of inks.

If desired, the counterions associated with the surface-modifying groupsas a result of the sulfonation/oxidation process may be exchanged orsubstituted with other suitable cations using known ion-exchangetechniques such as ultrafiltration, reverse osmosis, conversion to acidform as an intermediate, and the like. Examples of suitable cations thatmay be exchanged include, but are not limited to, alkali metal ions(e.g., K⁺ and Li⁺), alkaline earth metals (e.g., Ca²⁺, Mg²⁺ and Ba²⁺)and NR₁R₂R₃H⁺ wherein R₁, R₂ and R₃ may independently be H or C₁-C₈alkyl groups that may be unsubstituted or substituted. Exemplary cationsinclude, but are not limited to, tetraethylammonium, tetramethylammonium(TMA), ethanolammonium, triethanolammonium (TEA), monoethanolammonium(MEA), tetrabutylammonium (TBA), etc. In one embodiment, as representedby Example 19, the pKa differences between the surface carboxyl andsulfonyl groups can be beneficially exploited for partial exchange ofcounterions.

Properties of Modified Pigments

The method of modifying pigments by sulfonation and subsequent oxidationmay, but need not, provide several advantages over pigments that havebeen treated with sulfonation or oxidation alone. For example, themodified pigments of the present invention may exhibit greaterdispersability. As presented in the Examples section, Commercial pigmentred 122 was modified by sulfonation and oxidation (Examples 10-13),oxidation only (Comparative Example 1) and sulfonation only (ComparativeExample 2). The comparative examples are disclosed in U.S. Pat. Nos.6,596,068 and 6,648,954, respectively. The oxidized pigment inComparative Example 1 began to settle upon standing within three days atambient temperature. The sulfonated pigment in Comparative Example 2exhibited hard settling in the bottom of a container after setting forone week in an oven at 70° C. In contrast, the sulfonated/oxidizedpigments of Examples 10-13 exhibited no observable settling aftersetting for two weeks at 70° C. More generally, the dispersions of thepresent invention may not settle for at least about 1 week, moreparticularly at least about 3 weeks, and even more particularly at leastabout 4 weeks when stored at 70° C.

Other advantages may include a greater concentration of surfacemodifying groups. Example 22 contrasts the TGA spectra for a sulfonated,carboxy modified carbon black (obtained from the procedure of Example 7)with a carboxy modified carbon black (i.e., Sensijet Black SDP 1000,available from Sensient Colors, Inc., St. Louis, Mo.). Both modifiedcarbon blacks exhibit three distinct weight loss regions. Thesulfonated, carboxy modified carbon black exhibits a weight lossequivalent to 1424 μMoles CO₂ per gram of pigment from 103-313° C. Incontrast, the carboxy modified carbon black exhibits a weight lossequivalent to 1239 μMoles CO₂ per gram of pigment from 101-308° C. Thegreater weight loss equivalent over similar temperature ranges for thecarboxy modified carbon black suggests a greater concentration ofsurface modifying groups when compared to the carboxy modified carbonblack.

Modified pigments of the present invention in an aqueous dispersion takeup about 0.1 to about 1.7 mMoles of HCl when titrated with 2.0 N HCl. Inthe case of carbon black, this range is typically about 1.4 to about 1.7mMoles of HCl when titrated with 2.0 N HCl, as represented in Example23.

Carbon black modified according to the present invention may compriseabout 0.3 to about 1.0 mMoles of S per gram of pigment, particularlyabout 0.5 to about 0.8 mMoles of S per gram of pigment. Colored pigmentsother than carbon black (such as yellow, magenta and cyan) may compriseabout 0.02 to about 0.9 mMoles of S per gram of pigment, particularlyabout 0.03 to about 0.2 mMoles of S per gram of pigment.

The modified carbon black may comprise about 1.0 to about 2.0 mMoles ofactive hydrogen per gram of pigment, particularly about 1.5 to about 1.8mMoles of active hydrogen per gram of pigment. Colored pigments otherthan carbon black (such as yellow, magenta and cyan) may comprise about0.2 to about 1.5 mMoles of active hydrogen per gram of pigment,particularly about 0.3 to about 1.0 mMoles of active hydrogen per gramof pigment.

Dispersions of the present invention may have viscosities ranging fromabout 1.5 to about 3.0 cP, particularly about 1.8 to about 2.6 cP.Surface tensions may range from about 60 dynes/cm to about 72 dynes/cm,particularly about 67 dynes/cm to about 72 dynes/cm. pH values may rangefrom about 7 to about 9, particularly about 7.4 to about 8.5.

The self-dispersing pigments of the present invention may also exhibitlong-term and high temperature stability, higher water and highlighterresistance than expected of a pigment with attached sulfonic orcarboxylic acid groups, and have particle size distributions comparableto products typically obtained only after particle reduction processessuch as “milling”.

The modified pigments according to the present invention may be used ina number of end use applications. These uses include, but are notlimited to, coatings, paints, papers, adhesives, latexes, toners,textiles, fibers, plastics and inks. The modified pigments produced bythe process of the invention are particularly well-suited for use ininkjet inks.

Ink Jet Inks

Another aspect of the present invention relates to inkjet inkformulations using the surface-modified pigments described above. Inkjetformulations comprising such modified pigments or dispersions comprisingsuch modified pigments may do at least one of the following: 1) provideuniform, bleed-free images, when printed both on a plain and colorbackground, with high resolution and high density on print media; 2) notcause nozzle clogging which typically occurs due to drying of the ink ata distal end of a nozzle; 3) rapidly dry on paper; 4) exhibit good lightresistance and water resistance; 5) demonstrate good long-term storagestability; 6) demonstrate print characteristics which are independent ofthe paper quality; and 7) provide resistance to highlighter afterprinting.

The ink compositions of the present invention may be prepared bycombining the above modified pigments with an aqueous vehicle and anysuitable additives. The amount of modified pigment (by weight) in theink composition is suitably at least about 0.1%, particularly at leastabout 1.5%, particularly at least about 2.0%, and more particularly atleast about 2.5% or about 5.0%. Furthermore, the amount of modifiedpigment (by weight) in the ink composition is less than or equal toabout 12% or about 10%, particularly less than or equal to about 10% orabout 8%, and more particularly less than or equal to about 5.5% orabout 5%. This includes embodiments where the amount of modified pigment(by weight) in the ink composition is present in an amount ranging fromabout 0.5% to about 10%, and an amount ranging from about 2% to about5%.

The aqueous vehicle may comprise water or water in combination with oneor more water-soluble organic solvents. The type of water used in theink compositions is not limited. However, distilled water, deionizedwater, super pure water, and ultrafiltrate may be used to minimize theintroduction of impurities. The water may also be sterilized by UVradiation and/or the addition of hydrogen peroxide. The amount of water(by weight) in the ink composition is at least about 40%, particularlyat least about 50%, and more particularly at least about 60%.Furthermore, the amount of water (by weight) in the ink composition isless than or equal to about 90%, particularly less than or equal toabout 85%, and more particularly less than or equal to about 80% orabout 70%. This includes embodiments where the amount of water (byweight) in the ink composition is about 40% to about 85%.

Water-soluble organic solvents may be combined with water to make up theaqueous vehicle. Water-soluble organic solvents may include alcoholshaving 1 to 5 carbon atoms, such as methyl alcohol, ethyl alcohol,n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol,tert-butyl alcohol, isobutyl alcohol and n-pentanol; polyhydric alcoholssuch as ethylene glycol, diethylene glycol, triethylene glycol,propylene glycol, dipropylene glycol, tripropylene glycol, 1,3-propyleneglycol, isopropylene glycol, butylene glycol, isobutylene glycol,1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol,1,2-hexanediol, 1,2,6-hexanetriol, trimethylolpropane, glycerin,polyethyleneglycol, mesoerythritol and pentaerythritol; ketones andketone alcohols such as acetone and diacetone alcohol; ethers such astetrahydrofuran and dioxane; lower alkyl ethers of polyhydric alcohols,such as ethylene glycol monomethyl (or monoethyl)ether, diethyleneglycol monomethyl (or monoethyl)ether and triethylene glycol monomethyl(or monoethyl)ether; lower dialkyl ethers of polyhydric alcohols, suchas triethylene glycol dimethyl (or diethyl)ether and tetraethyleneglycol dimethyl (or diethyl)ether; nitrogen-containing solvents such aspyrrolidone, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone,cyclohexylpyrrolidone, monoethanolamine, diethanolamine,triethanolamine, dimethylformamide and dimethylacetamide;sulfur-containing solvents such as thiodiethanol, thiodiglycerol,sulfolane, and dimethylsulfoxide; propylene carbonate, and ethylenecarbonate, sugars and derivatives thereof such as glucose, fructose,galactose, mannose, and xylose; sugar-alcohols; an oxyethylene adduct ofglycerin; and an oxyethylene adduct of diglycerin. The water-solubleorganic solvents may be used alone or in combination. If a mixture ofwater and a water-soluble organic solvent is used, the amount ofwater-soluble organic solvent (by weight) in the ink composition is atleast about 1% or about 5%, particularly at least about 15%, and moreparticularly at least about 20% or about 25%. Furthermore, the amount ofwater-soluble organic solvent (by weight) in the ink composition is lessthan or equal to about 80% or about 50%, particularly less than or equalto about 60% or about 30%, and more particularly less than or equal toabout 40% or about 15%. This includes embodiments where the amount ofwater-soluble organic solvent (by weight) in the ink composition isabout 5% to about 30%, and more preferably about 1% to about 25%.

Additives may be incorporated into the aqueous vehicle to impart anynumber of desired properties, such as might be needed to adapt the inkto the requirements of a particular inkjet printer or to provide abalance of light stability, smear resistance, viscosity, surfacetension, coating penetration, optical density, adhesion, highlighterresistance or crust resistance. Penetrants, for example, may be added toreduce bleed, improve wetting of the print media, and otherwise improveoverall performance of the print image. Examples of penetrants mayinclude, but are not limited to, alkyl alcohols having 1 to 4 carbonatoms, such as ethanol, methanol, butanol, propanol and isopropanol;glycol ethers, such as ethylene glycol monomethyl ether, ethylene glycolmonoethyl ether, ethylene glycol monobutyl ether, ethylene glycolmonomethyl ether acetate, diethylene glycol monomethyl ether, diethyleneglycol monoethyl ether, diethylene glycol mono n-propyl ether, ethyleneglycol mono isopropyl ether, diethylene glycol mono isopropyl ether,ethylene glycol mono n-butyl ether, ethylene glycol mono t-butyl ether,diethylene glycol mono t-butyl ether, 1-methyl-1-methoxy butanol,propylene glycol monomethyl ether, propylene glycol monoethyl ether,propylene glycol mono t-butyl ether, propylene glycol mono n-propylether, propylene glycol mono isopropyl ether, dipropylene glycolmonomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycolmono n-propyl ether, and dipropylene glycol mono isopropyl ether,diethylene glycol butyl ether, butyl oxitol glycol ether; diols, such as1,2-alkyl diols; formamide; acetamide; dimethylsulfoxide; sorbitol;sorbitan; acetin; diacetin; triacetin; and sulfolane. The penetrants maybe used alone or in combination. The amount of penetrant (by weight) inthe ink composition ranges from 0% to about 60%, particularly from about0% or about 2% to about 40%, and more particularly from about 0.5% toabout 15%, or from about 5% to about 20%, or from about 10% to about15%.

Surfactants may be added to the aqueous medium to reduce the surfacetension of the ink composition. The surfactants may be anionicsurfactants, non-ionic surfactants and/or cationic surfactants. Suitablesurfactants may include those listed below and in U.S. Pat. No.5,116,409 issued May 26, 1992, U.S. Pat. No. 5,861,447 issued Jan. 19,1999, and U.S. Pat. No. 6,849,111 issued Feb. 1, 2005, each of which ishereby incorporated by reference.

The anionic surfactants may include alkylbenzene sulfonate, analkylphenyl sulfonate, an alkylnaphthalene sulfonate, a higher fattyacid salt, a sulfate ester of a higher fatty acid ester, a sulfonate ofa higher fatty acid ester, a sulfate ester and a sulfonate of a higheralcohol ether, a higher alkylsulfosuccinate, a polyoxyethylenealkylether carboxylate, a polyoxyethylene alkylether sulfate, analkylphosphate, and a polyoxyethylene alkylether phosphate. Specificexamples of the anionic surfactant include dodecylbenzene sulfonate,isopropylnaphthalene sulfonate, monobutylphenylphenol sulfonate,monobutylbiphenyl sulfonate, monobutylbiphenyl sulfonate, anddibutylphenylphenol disulfonate.

The nonionic surfactants may include a polyoxyethylene alkyl ether, apolyoxyethylene alkyl phenyl ether, a polyoxyethylene fatty acid ester,a sorbitan fatty acid ester, a polyoxyethylene sorbitan fatty acidester, a polyoxyethylene sorbitol fatty acid ester, a glycerin fattyacid ester, a polyoxyethylene glycerin fatty acid ester, a polyglycerinfatty acid ester, a cane sugar fatty acid ester, a polyoxyethylenealkylamine, a polyoxyethylene fatty acid amide, an alkylalkanolamide, apolyethylene glycol polypropylene glycol block copolymer, acetyleneglycol, and a polyoxyethylene adduct of acetylene glycol, and specificexamples of the nonionic surfactant include polyoxyethylene nonyl phenylether, polyoxyethylene octyl phenyl ether, polyoxyethylene dodecylphenyl ether, a polyoxyethylene alkyl ether, a polyoxyethylene fattyacid ester, a sorbitan fatty acid ester, a polyoxyethylene sorbitanfatty acid ester, fatty acid alkylolamide, a polyethyleneglycol/polypropylene glycol block copolymer, acetylene glycol, and apolyoxyethylene adduct of acetylene glycol.

Specific examples of the water-soluble cationic surfactants used in thepresent invention may include inorganic or organic acid salts of analiphatic primary amine such as octylamine, laurylamine, stearylamine,oleylamine, tetradecylamine, hexadecylamine, coconut amine, coconutalkylamine, tallow amine, cured tallow alkylamine, soybean alkylamineand the like; inorganic or organic acid salts of an aliphatic secondaryamine such as distearylamine, dioleylamine, di-coconut alkylamine,di-cured tallow alkylamine and the like; inorganic or organic acid saltsof aliphatic tertiary amine such as dimethyloctylamine,dimethyldecylamine, dimethylaurylamine, dimethylmyristylamine,dimethylpalmitylamine, dimethylstearylamine, dilaurylmonomethylamine,dioleylmonomethylamine, trioctylamine, dimethyl coconut amine, coconutalkyldimethylamine, tallow alkyldimethylamine, cured tallowalkyldimethylamine, soybean alkyldimethylamine, di-coconutalkylmonomethylamine, di-cured tallow alkylmonomethylamine and the like;aliphatic quaternary ammonium salts such as tetramethylammoniumchloride, tetraethylammonium chloride, tetrapropylammonium chloride,tetrabutylammonium chloride, lauryltrimethylammonium chloride,trioctylmethylammonium chloride,3-chloro-2-hydroxypropyltrimethylammonium chloride,docosenyltrimethylammonium chloride, hexadecyltrimethylammoniumchloride, octadecyltrimethylammonium chloride, coconutalkylrimethylammonium chloride, tallow alkyltrimethylammonium chloride,octadecyldimethyl (3-trimethoxysilylpropyl)ammonium chloride and thelike; aromatic quaternary ammonium salts such as benzyltrimethylammoniumchloride, benzyltriethylammonium chloride, benzyltributylammoniumchloride, benzyltrimethylammonium chloride, phenyltrimethylammoniumchloride, cetyldimethylbenzylammonium chloride and the like; pyridiniumsalt type compounds (e.g., octylpyridinium chloride, cetylpicoliniumchloride), imidazoline type cationic compounds (e.g.,2-heptadecenyl-hydroxyethylimidazolium chloride), benzotonium chloride,ethylene oxide added type quaternary ammonium salts (e.g.,polyoxyethylenetrimethylammonium chloride), hydrochloride or acetate ofaliphatic amides; salt of polyethylenepolyamine aliphatic amides; saltof urea condensate of polyethylenepolyamine aliphatic amides; quaternaryammonium salt of urea condensate of polyethylenepolyamine aliphaticamides; and N,N-dialkylmorphonium salts; and the like.

Other surfactants include a silicone surfactant such as an oxyethyleneadduct of polysiloxane, a fluorinated surfactant such as aperfluoroalkylcarboxylate, a perfluoroalkylsulfonate, or anoxyethyleneperfluoroalkyl ether. A biosurfactant such as spicrispolicacid, rhamnolipid, or lysolecithin can also be used.

Among the above described surfactants, surfactants each having anunsaturated bond and surfactants each having a secondary or tertiaryalkyl group may be used. Examples of the surfactant each having anunsaturated bond include alkyl ether derivatives of unsaturated alcoholssuch as oleyl alcohol, elaidyl alcohol, linoleyl alcohol, linolenylalcohol, 2-heptanedecene-1-ol, and acetylene alcohol; and alkyl esterderivatives of unsaturated fatty acids such as lauroleic acid,myristoleic acid, oleic acid, linoleic acid, linolenic acid, dodecynoicacid, and octadecynoic acid.

Examples of the surfactant each having secondary or tertiary alkyl groupinclude alkyl ether derivatives of branched alcohols such as2-ethylhexyl alcohol, 2-octanol, 2-hexadecanol, and 2-octadecanol; andalkyl esters of branched fatty acids such as methylheptadecanoic acid,methylpentadecanoic acid, and methyloctadecanoic acid.

Surfactants are commercially available under various well-knowntradenames, such as the PLURONIC® series (BASF Corporation, Parsippany,N.J.), the TETRONIC® series (BASF Corporation, Parsippany, N.J.), theARQUAD® series (Akzo Chemical Inc., Chicago, Ill.), the TRITON® series(Union Carbide Corp., Danbury, Conn.), the SURFONIC® series (TexacoChemical Company, Houston, Tex.), the ETHOQUAD® series (Akzo ChemicalInc., Chicago, Ill.), the ARMEEN® series (Akzo Chemical Inc., Chicago,Ill.), the ICONOL® series (BASF Corporation, Parsippany, N.J.), theSURFYNOL® series (Air Products and Chemicals, Inc. Allentown, Pa.), andthe ETHOMEEN® series (Akzo Chemical Inc., Chicago, Ill.), to name a few.

The surfactants may be used alone or in combination. The amount ofsurfactant (by weight) in the ink composition may range from 0% to about10%, particularly from about 0.1% to about 3%, and more particularlyfrom about 0.05 or about 1.5% to about 3% or about 5%. This includesembodiments where the amount of surfactant (by weight) in the inkcomposition may range from about 0% or about 0.1% to about 8%.

One or more humectants may be added to the aqueous vehicle to preventclogging, caused by drying out during periods of latency, of inkjetnozzles. Humectants may be selected from materials having highhygroscopicity and water-solubility. Examples of humectants include, butare not limited to, polyols such as glycerol, ethylene glycol,diethylene glycol, triethylene glycol, tetraethylene glycol,polyethylene glycol, propylene glycol, dipropylene glycol, polypropyleneglycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol,1,3-butanediol, 2,3-butanediol, 1,4-butanediol, 1,5-pentanediol,1,6-hexanediol, 1,8-octanediol, 1,2,4-butenetriol, 1,2,6-hexanetriol andpentaerythritol; lactams such as 2-pyrrolidone, 1-methyl-2-pyrrolidone,N-methyl-2-pyrrolidone and ε-caprolactam; urea compounds such as urea,thiourea, ethyleneurea and 1,3-dimethylimidazolidinone; saccharides suchas maltitol, sorbitol, gluconolactone and maltose;1,4-cyclohexanedimethanol; 1-methyl-2-piperidone; N-ethylacetamide;N-methylpropionamide; N-acetyl ethanolamine; N-methylacetamide;formamide; 3-amino-1,2-propanediol; 2,2-thiodiethanol;3,3-thiodipropanol; tetramethylene sulfone; butadiene sulfone; ethylenecarbonate; butyrolacetone; tetrahydrofurfuryl alcohol; trimethylpropane;pantothenol and Liponic EG-1. There are no particular limitations on theamount used of the humectant, but in general the amount of humectant (byweight) in the ink composition may range from 0% to about 30%,particularly from about 1% to about 15% or about 20%, and moreparticularly from about 4% or about 5% to about 10% or about 15%.

Polymers may be added to the ink composition to improve the waterresistance, rub resistance and highlighter resistance of the images onprint media. Suitable polymers may include, but are not limited to,polyvinyl alcohol, polyester, polyestermelamine, styrene-acrylic acidcopolymers, styrene-maleic acid copolymers, styrene-maleic acid-alkylacrylate copolymers, styrene-metacrylic acid copolymers,styrene-metacrylic acid-alkyl acrylate copolymers, styrene-maleic halfester copolymers, vinyl-naphthalene-acrylic acid copolymers, vinylnaphthalene-maleic acid copolymers and salts thereof. Additionalpolymers include polyvinylimidazole, derivatives of polyvinylimidazole,copolymers of vinylimidazole, copolymers of vinylimidazole derivatives,polyvinylpyridine, derivatives of polyvinylpyridine, copolymers ofvinylpyridine, copolymers of vinylpyridine derivatives,polyethyleneimine, and derivatives of polyethyleneimine. The polymersmay be used alone or in combination. The amount of polymer (by weight)in the ink composition may range from 0% to about 5%, particularly fromabout 0.1% to about 3%, and more particularly from about 0.2% to about2.5%. This includes embodiments where the amount of polymer (by weight)in the ink composition may range from about 0% or about 0.1% to about3.0%.

Ink compositions of the present invention may be buffered to a desiredpH using any number of pH modifiers. Suitable pH modifiers may includealkali hydroxides (e.g., sodium hydroxide, lithium hydroxide andpotassium hydroxide), alkali carbonates and bicarbonates (e.g., sodiumcarbonate and sodium bicarbonate), ammonium hydroxide, potassiumhydrogenphthalate, potassium dihydrogenphosphate, sodiumdihydrogenphosphate, sodium tetraborate, potassium hydrogen tartrate,sodium hydrogen carbonate, tris(hydroxymethyl)aminomethane, andtris(hydroxymethyl)aminomethane hydrochloride, triethylamine,dimethylethanolamine, triethanolamine, mineral acids, hydrochloric acid,and sulfuric acid. The pH modifiers may be used alone or in combination.The amount of pH modifier (by weight) in the ink composition may rangefrom 0% to about 3.0%, particularly from about 0.1% to about 2.0%, andmore particularly from about 0.05% or about 0.5% to about 1.0% or about1.5%. This includes embodiments where the amount of pH modifier (byweight) in the ink composition ranges from about 0.05% or about 0.2% toabout 1.5% or about 2.5%.

Preservatives, such as biocides and fungicides, may also be added to theink composition. Examples of suitable preservatives include sodiumbenzoate, pentachlorophenol sodium, 2-pyridinethiol-1-oxide sodium,sodium sorbate, sodium dehydroacetate, benzisothiazolinone,1,2-dibenzothiazolin-3-one, methylisothiazolinone andchloromethylisothiazolinone. Commercially available biocides includeUCARCIDE® 250 (available from Union Carbide Company), Proxel® CRL,Proxel® BDN, Proxel® GXL, Proxel® XL-2, Proxel® TN (available from ArchChemicals, Smyrna, Ga.), Dowicides® (Dow Chemical, Midland, Mich.),Nuosept® (Huls America, Inc., Piscataway, N.J.), Omidines® (Olin Corp.,Cheshire, Conn.), Nopcocides® (Henkel Corp., Ambler, Pa.), XBINX® 119G(PMC Specialties Group, Inc., Cincinnati, Ohio), Bioban™ (available fromDow Chemical, Midland, Mich.), and Troysans® (Troy Chemical Corp.,Newark, N.J.). The preservatives may be used alone or in combination.The amount of preservatives (by weight) in the ink composition may rangefrom 0% to about 1.5%, particularly from about 0.05% to about 1.0%, andmore particularly from about 0.1% to about 0.3%. This includesembodiments where the amount of preservative (by weight) in the inkcomposition may range from about 0.05% to about 0.5%.

The ink composition may contain one or more viscosity modifiers.Viscosity modifiers may include rosin compounds, alginic acid compounds,polyvinyl alcohol, hydroxypropyl cellulose, carboxymethyl cellulose,hydroxyethyl cellulose, methyl cellulose, salts of polyacrylic acid,polyvinyl pyrrolidone, gum Arabic and starch. The amount of viscositymodifier (by weight) in the ink composition may range from 0% to about10%, particularly from about 0.5% to about 8%, and more particularlyfrom about 1% to about 5%. This includes embodiments where the amount ofviscosity modifier (by weight) in the ink composition may range fromabout 0% or about 1% to about 7%.

Other additives which may be incorporated into the aqueous vehicle mayalso include antioxidants, ultraviolet absorbers, chelating agents,corrosion inhibitors, electric conductivity adjusters, viscositymodifiers, oxygen absorbers, anti-kogation agents, anti-curling agents,anti-bleed agents, defoamers, and buffers.

Examples of suitable corrosion inhibitors may include, withoutlimitation, acidic sulfite, sodium thiosulfate, ammonium thioglycolate,diisopropyl ammonium nitrite, pentaerythritol tetranitrate, dicyclohexylammonium nitrite, benzotriazole, tolyltriazole, carboxybenzotriazole,and sodium tolytriazole. The corrosion inhibitors may be used alone orin combination. The amount of corrosion inhibitor (by weight) in the inkcomposition may range from 0% to about 1.0%, particularly from about0.05% to about 0.5%, and more particularly from about 0.1% to about0.3%.

The ink compositions of the present invention may contain one or morecolorants in addition to the pigment dispersion of the presentinvention. Such colorants can be selected from the group of pigments anddyes generally useful in inkjet printing. Examples of such dyes mayinclude, but are not limited to, C. I. Direct Black 17, 19, 32, 51, 71,108, 146, 154, 168; C. I. Direct Blue 6, 22, 25, 71, 86, 90, 106, 199;C. I. Direct Red 1, 4, 17, 28, 83, 227; C. I. Direct Yellow 12, 24, 26,86, 98, 132, 142; C. I. Direct Orange 34, 39, 44, 46, 60; C. I. DirectViolet 47, 48; C. I. Direct Brown 109; C. I. Direct Green 59; C. I. AcidBlack 2, 7, 24, 26, 31, 52, 63, 112, 118; C. I. Acid Blue 9, 22, 40, 59,93, 102, 104, 113, 117, 120, 167, 229, 234; C. I. Acid Red 1, 6, 32, 37,51, 52, 80, 85, 87, 92, 94, 115, 181, 256, 289, 315, 317; C. I. AcidYellow 11, 17, 23, 25, 29, 42, 61, 71; C. I. Acid Orange 7, 19; and C.I. Acid Violet 49. The dyes as described above may be used singly.Alternatively, two or more of the dyes as described above may be used incombination.

Any one of the organic pigments may be used as a colorant. The pigmentis not specifically limited. Examples of such pigments may include, butare not limited to, carbon black, azo pigment, phthalocyanine pigment,anthraquinone pigment, quinacridone pigment, thioindigo pigment,triphenylmethane lake pigment, and oxazine lake pigment. Specifically,those having yellow colors include, for example, C. I. Pigment Yellow 1,2, 3, 4, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 19, 65, 74, and 83 andSolvent Yellow 33. Those having red colors include, for example, C. I.Pigment Red 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17,18, 19, 21, 22, 23, 30, 31, 32, 37, 38, 39, 40, 49, 50, 51, 52, 53, 55,60, 64, 83, 87, 88, 89, 90, 112, 114, 122, 123, and 163. Those havingblue colors include, for example, C. I. Pigment Blue 2, 3, 15, 16, 22,and 25. Those having black colors include, for example, C. I. PigmentBlack 1 and 7. Those capable of self dispersion, which are subjected tothe surface-modifying treatment and which can be stably dispersed evenwhen no dispersing agent is used, are preferred as the pigment.

The ink compositions of the present invention may be formulated using avariety of methods known in the art. In one embodiment, the inks may beformulated using a two vessel method. In this method, a first vessel isused to make the ink base or diluent. A second vessel is used to slowlydilute the pigmented dispersion during a process commonly called a“letdown.” The equipment used in the method of making the ink may beglass, polypropylene, polyethylene, or stainless steel. Other materialsthat are inert to the ink ingredients may also be used.

First, the appropriate amount of water is added to the first vessel. Amixing device is then placed inside the vessel to agitate the water andprovide mixing while the other ingredients are added. Mixing may beachieved either by a magnetic stirring mechanism or a motor drivenstirring blade. Any chelating agents are then added to the first vesseland allowed to dissolve prior to the addition of any co-solvents. Next,any desired co-solvents are added and allowed to dissolve. Any desiredpH modifiers may then be added and are allowed to dissolve. Finally, anyother functional ingredients that may be desired, including, withoutlimitation, surfactants and corrosion inhibitors, may be added and areallowed to dissolve.

The second vessel is prepared by adding the appropriate amount of thepigment dispersion to the vessel. A mixing device is then placed intothe vessel. After all of the ingredients in the diluent have dissolved,the diluent is slowly added to the pigment dispersion in the secondvessel. The dispersion is mixed during this process. In anotherembodiment, the pigment dispersion is slowly added to the diluent. Afterall of the diluent or dispersion has been added, the ink is mixed forabout 15 minutes to about 1 hour, or until it is completely homogenous.After mixing, the ink is filtered.

The ink compositions of the present invention are particularly suitedfor use as an ink composition for inkjet printing wherein droplets ofthe ink composition are ejected from a printing apparatus and depositedonto a substrate to generate an image. Suitable printing apparatusinclude, but are not limited to, Continuous Ink Jet (CIJ),prop-on-Demand Valve (DoD Valve), prop-on-Demand Piezo-Electric (DoDPiezo), Memjet and Thermal Ink Jet (TIJ). Similarly, any suitablesubstrate may be employed including plain papers, bonded papers, coatedpapers, transparency materials, textile materials, plastics, polymericfilms and inorganic substrates. However, it should be recognized bythose skilled in the art that the above ink compositions may also haveuse in other applications including, but not limited to, general writingutensil applications and stamp applications.

The black ink compositions of the present invention may be used alone,or with a color underlay, to produce a black image or in combinationwith other ink compositions to produce a color image. In someembodiments, the ink composition of the present invention is used incombination with other ink composition(s), such as a black ink, a cyanink, a magenta ink and/or a yellow ink. In other embodiments, a cyanink, a magenta ink and a yellow ink are overprinted to form a blackimage and this printing is used in combination with the printing of theblack ink of the present invention.

The ink compositions of the present invention may have certain printperformance characteristics. These print performance characteristics aremeasured in the following manner.

Print Performance Testing:

Water Resistance Procedure. Spectrodensitometer Procedure.

To test water resistance, a sample that is one half inch wide by threeinches long is prepared. The top half is left unprinted while the bottomhalf is printed with the ink of interest. Using an X-Rite 938spectrodensitometer with a D65 illuminant and 10 degrees standardobserver (available from X-Rite Inc., Grand Rapids, Mich.), the printedblock portion of the sample is scanned for initial optical densityreading. The printer block half of the sample is submerged under DIwater for 60 seconds. The sample is removed and laid down to drycompletely on a hard surface. The sample is rescanned for soaked opticaldensity reading. The data is recorded as the difference in opticaldensity readings.

The black and color ink compositions of the present invention may have awater resistance value (measured as the difference in optical density)of about 0.00 to about 2.00, preferably a value of about 0.00 to about0.20, and more preferably a value of less than about 0.05.

Highlighter Resistance Procedure. Spectrodensitometer Procedure.

A printed test image with a black or colored box two inches wide isprepared. Even pressure is applied on the highlighter and moved back andforth in blank portion of the page to create a baseline highlightedsection. The procedure is repeated moving back and forth in and out ofthe black or colored box. An X-Rite 938 spectrodensitometer with a D65illuminant and 10 degrees standard observer is used, scanning both inthe highlighter baseline area and next to the black or colored box wherethe highlighter is passing. The data is recorded as the difference inoptical density readings.

The black ink compositions of the present invention may have ahighlighter resistance value (measured as the difference in opticaldensity) of about 0.00 to about 2.00, preferably a value of about 0.00to about 0.10, and more preferably a value of less than about 0.04.

The color ink compositions of the present invention may have ahighlighter resistance value (measured as the difference in opticaldensity) of about 0.00 to about 0.10, and more preferably a value ofless than about 0.04.

Rub Resistance Procedure: Sutherland Rub Tester 2000 (available fromDanilee Company, San Antonio, Tex.), 100 cycles, Speed 1, 8 Samples, 4lb, Test Pattern 9 from RFver 1.4 test file. SpectrodensitometerProcedure.

A printed test image with a black or colored box two inches wide isprepared. A wadded up delicate lab tissue is used to apply even pressureand is rubbed back and forth in and out of the black or colored box. AnX-Rite 938 spectrodensitometer with a D65 illuminant and 10 degreesstandard observer is used to scan both a blank section of the page as abaseline and next to the black or colored box where the rubbingoccurred. The data is recorded as the difference in optical densityreadings.

The black and color ink compositions of the present invention may have arub resistance value (measured as the difference in optical density) ofabout 0.00 to about 2.00, preferably a value of about 0.00 to about0.25, and more preferably a value of less than about 0.10.

ImageXpert Instrument Procedure [Line Width, Edge Acuity, IntercolorBleed, Mottle].

The ImageXpert SN1 test image is printed. ImageXpert Xaminer JR software(available from ImageXpert, Nashua, N.H.) is used to scan horizontal andvertical line widths, edge acuity, intercolor bleed, and mottle. Theline widths and edge acuity are recorded in microns. Mottle is recordedas the standard deviation from the gray average density from the solidcolor block of interest.

The black and color ink compositions of the present invention may havean edge acuity value of about 0 microns to about 50 microns, and morepreferably a value of less than about 25 microns.

The black and color ink compositions of the present invention may have aline width value of about 200 microns to about 350 microns, and morepreferably a value of about 225 microns to about 300 microns.

The black and color ink compositions of the present invention may have ableed value of about 0 microns to about 100 microns, and more preferablya value of less than about 25 microns.

The black ink compositions of the present invention may have a mottlevalue of about 0.00 to about 3.00, and more preferably a value of lessthan about 1.75.

The color ink compositions of the present invention may have a mottlevalue of about 0.00 to about 6.00, and more preferably a value of lessthan about 2.00.

Optical Density Procedure

Optical density (OD) is recorded using an X-Rite 938spectrodensitometer. The OD is measured by supplying the standardilluminant D65 at 0 degrees from the ink sample. Reflectance is measuredat 45 degrees from the ink sample. OD is calculated as the negative logof the percent reflected from the ink sample. D65 standard illuminant isdefined under the CIE (Commission Internationale de l'eclairage).

The black and color ink compositions of the present invention may havean optical density (measured as the negative log of reflectance) ofabout 1.00 to about 3.00, and more preferably a value of about 1.30 toabout 2.00.

CIE L*a*b* Color Space Coordinates Procedure

An X-Rite 938 spectrodensitometer is used to measure the color spacecoordinates. The D65 illuminant is used, and 0/45 degree angles from thelight source to the sensor are used. In addition, when taking thesemeasurements using the spectrodensitometer, the “CIE 1964 10 degreestandard observer” is used in the color translation.

Cartridge Start-Up Procedure

Cartridge start-up is used to assess the printability of the ink in thecartridge. The ink is initially printed. Next, the cartridge is allowedto sit in ambient conditions for 3 days, without protecting the printhead. The cartridge is then placed back into the printer and the ink isagain printed. The prints are visually assessed for feathering, mottle,banding, or lining that appears.

Light Resistance Procedure

Light resistance is a measure of a sample before and after some exposurefor an amount of time. The length of time is the same for each samplemeasured in the experiment. The length of time between experiments canvary from 120 hours to 168 hours of exposure. The samples are exposed toa 765 watts/m² xenon arc lamp in the Suntest CPS+ fadeometer (availablefrom Atlas Material Testing Technology, Chicago, Ill.). The spectraldistribution of the xenon arc lamp is altered using Atlas' Indoor Lightfilter to simulate indoor light spectral distribution.

A CPS+ fadeometer (available from Atlas Material Testing Technology,Chicago, Ill.) is used to measure the CIE L*a*b* coordinates of thesamples before and after exposure. The distance between the two colorspace coordinates (ΔE) is calculated by the Pythagorean theorem andexpanded for three dimensions.

ΔE=√{square root over ((L1+L2)²+(a1+a2)²+(b1+b2)²)}{square root over((L1+L2)²+(a1+a2)²+(b1+b2)²)}{square root over((L1+L2)²+(a1+a2)²+(b1+b2)²)}, where L1, a1, and b1 refer to the firstset of L*a*b* coordinates, and L2, a2, and b2 refer to the second set ofL*a*b* coordinates.

Heat at 70° C.—Particle Count Procedure

The ink sample is heated to 70° C. and the particles are countedinitially, at one week, and at 23 days. The particle size is measuredusing an Accusizer 780A instrument (available from Partical SizingSystems, Santa Barbara, Calif.). Pigmented ink flows through a small“photozone.” A “photozone” is a narrow region of uniform illuminationproduced by light from a laser diode.

0.3 mL of the ink is dispensed into a 100 mL volumetric flask anddiluted to the mark with DI water. 0.2 mL of the product of the sampledilution is added to the sample vessel, which contains 60 mL of DIwater. The product of the sample dilution is well mixed with a stir barcontained in the sample vessel. The number of particles is calculatedusing the following formula:

$\frac{{\# \mspace{14mu} {of}\mspace{14mu} {Particles}} > {0.5\mspace{14mu} {µm}}}{{mL}\mspace{14mu} {ink}} = \frac{\begin{matrix}{\left( {{{average}\mspace{14mu} {cumulative}\mspace{14mu} \# \mspace{14mu} {of}\mspace{14mu} {particles}} > {0.5\mspace{14mu} {µm}}} \right)*} \\{{dilution}\mspace{14mu} {factor}*\frac{100\mspace{14mu} {mL}\mspace{14mu} {sample}\mspace{14mu} {flask}}{\left( {0.2\mspace{14mu} {mL}*0.3\mspace{14mu} {mL}} \right)}}\end{matrix}}{\% \mspace{14mu} {solids}\mspace{14mu} {of}\mspace{14mu} {original}\mspace{14mu} {sample}}$

Freeze/Thaw/Heat Cycles Procedure

A 100 gram sample of the pigmented ink is prepared. First, the sample isfrozen at −15° C. for 8 hours. It is then thawed at room temperature foranother 8 hours. Finally, the sample was heated in an oven at 70° C. for8 hours. These three steps constitute a single cycle. The cycle isrepeated three times. The change in the particle size between theinitial sample and the sample after three cycles was measured using anAccusizer 780A instrument.

Examples of papers on which the above-identified tests can be conductedare HP

Multipurpose (20 lb weight, 92 brightness value), HP MultipurposeColorLok (20 lb weight, 96 brightness value), Office Depot 104, Xerox4200 (20 lb weight, 92 brightness value), Epson Photo Paper GlossySO₄₁₆₄₉, Epson Premium Photo Paper Glossy 2041667 (68 lb weight), OfficeDepot Premium White Copy (20 lb weight, 92 brightness value), andHammerill Great White Copy (20 lb weight, 92 brightness value).

Paper Independence

The inks of the present invention work on a wide variety of papers. Inother words, the inks may work well independent of the particular paperbeing used. These inks exceed other inks containing polymer stabilizeddispersions and other dispersions containing modified pigments. Forexample, the inks may fall within the following tolerances for specifiedprint quality attributes across a wide range of plain paper, contrary toother inks:

Standard Deviation 95% Within Units Optical Density 0.08 0.16 Line Width11.44 22.88 Microns Mottle 0.35 0.70 Bleed 3.3 6.6 Microns

In one embodiment, the invention provides a method of making an ink, themethod comprising: sulfonating a pigment; oxidizing the pigment to forma modified pigment; and incorporating the pigment into an ink, whereinprints made from the ink will fall within at least one of the followingtolerances with a 95 percent confidence level, regardless of the type ofpaper on which the print is printed: an optical density of 0.16 (±0.08);line width of 22.88 microns (±11.44); mottle of 0.70 (±0.35); and bleedof 6.6 microns (±3.3).

EXAMPLES Dispersion Examples

Particle size for the below examples was determined according to thefollowing procedure. Samples comprising 8-15% solids were prepared bydiluting one drop of sample to 15 ml deionized water and loading into 1cm disposable cuvette, avoiding air bubbles. Malvern Zetasizer Nanoseries Model ZEN3600 was then used to measure mean particle size in thesample.

Example 1 Black Pigment Dispersion Sulfonation with Oleum

40 g of commercial furnace carbon black (available from ColumbianChemicals, Marietta, Ga.), with a primary particle size of 13 nm andCTAB surface area of 206 m²/g, were sulfonated with 20% oleum (200 g) at120° C. for 20 hours. The reaction mixture was cooled to 90° C. andquenched in water and ice, allowing the quench temperature to rise to65° C. The precipitated product was isolated by filtration and washedfree of dissolved material. The product cake (108 g) was then oxidizedwith sodium hypochlorite (lab grade from Fisher, 13% solution, 378 g)allowing the temperature due to exotherm to rise to 60° C. After holdingthe oxidation mixture at 60° C. for one hour, an additional 377 g ofsodium hypochlorite (13% solution) were added and the reaction mixturewas held at 60° C. for an additional hour. The reaction mixture wasallowed to settle and then filtered to obtain 86 g of cake. The cake wasre-dispersed in deionized water, and the pH of the dispersion wasadjusted to 9.0. The dispersion was milled with a Hockmeyer media mill(available from Hockmeyer Equipment Corp., Elizabeth City, N.C.) with0.3 mm YTZ media (available from Quackenbush Co., Inc., Crystal Lake,Ill.). The dissolved impurities were removed by ultrafiltration untileach of the chloride content and the sulfate content of the feed samplewas less than 50 ppm. The product was then concentrated to 8% solids andmixed with 0.3%, wt/wt Proxel GXL (available from Arch Chemicals,Smyrna, Ga.). Finally, the product was filtered through 0.7 micron GFfilter.

The resulting dispersion had a solids content of 8.3% and a pH of 9.0.An analysis of the components in the dispersion showed 3 ppm Cl, 38 ppmSO₄, 13 ppm Ca, 38 ppm Fe, 2 ppm Mg and 4249 ppm Na. The averageparticle size was 95.6 nm.

Example 2 Black Pigment Dispersion Sulfonation with a Mixture of Oleumand Sulfuric Acid

160 g of commercial gas carbon black (available from Degussa, Akron,Ohio), with a primary particle size of 20 nm and B.E.T surface area of150 m²/g, were sulfonated with 800 g of lab grade (95%) sulfuric acidand 800 g of 20% reagent grade oleum at 120° C. for 21 hours. Thereaction mixture was cooled to 60° C. and quenched in water and ice. Theprecipitated product was isolated by filtration and washed free ofdissolved material. The product cake (826 g) was then oxidized withapproximately 10.9% sodium hypochlorite solution (1461 g) for one hourat 80° C. to get a fine carbon suspension. The dissolved impurities wereremoved by ultrafiltration until each of the chloride content andsulfate content of the feed sample adjusted to 10% solids was less than100 ppm. The pH was adjusted to 7.5 with the addition of eitherhydrochloric acid or sodium hydroxide prior to completion of the abovenoted purification step. The product was then concentrated to 16% solidsand mixed with 0.3% wt/wt Proxel GXL (available from Arch Chemicals,Smyrna, Ga.). Finally, the product was filtered through a 0.7 micron GFfilter.

The resulting dispersion had a solids content of 16.1%, a viscosity of3.2 cP and a pH of 8.2. An analysis of the components in the dispersionshowed 6 ppm Cl, 71 ppm SO₄, 2.1 ppm Ca, 3.6 ppm Fe, 0.9 ppm Mg and 6571ppm Na. The average particle size was 116.5 nm.

Example 3 Black Pigment Dispersion Sulfonation with Sulfuric Acid

330 lbs of 99.4% sulfuric acid and 22 lbs of gas carbon black (availablefrom Degussa, Akron, Ohio), with 150 m²/g surface area and primaryparticle size of 20 nm, were combined in a 30 gallon Pfaudler reactorwith good mixing. Once the carbon was dispersed in the sulfuric acid,the mixture was heated to about 120° C. The reaction mixture was stirredfor about 20-24 hours while maintaining the temperature of the reactionmixture at about 120-125° C. Stirring was stopped and the reactor wasallowed to cool to about 60-65° C.

While the reactor was cooling, a quench tank was filled with about 100gallons deionized water and about 50 gallons ice to produce a deionizedwater/ice mixture. The quench tank was cooled to less than 10° C.

Once the reactor temperature reached about 60-65° C., the contents ofthe reactor were transferred to the quench tank slowly to avoidsplashing. The reactor was rinsed with deionized water and the rinsingswere added to the mixture in the quench tank. The mixture in the quenchtank was heated to about 20-25° C. The material from the quench tank wasfiltered through a filter press. The filtrate was recycled back to thequench tank until the quench tank was free of solids. The filteredcarbon sulfonation cake was washed with about 100 gallons of deionizedwater and the carbon sulfonation cake was dropped from the press. Thecarbon sulfonation cake at this point could be stored until ready foruse.

32.5 lbs of wet carbon sulfonation cake were combined with 60 lbs ofdeionized water and mixed overnight. The next day, the mixture wascooled to 30° C. and 16.5 lbs of sodium hydroxide (25% solution) wereadded to bring the pH up to about 11.9. The mixture was further cooledto 28° C., and 119 lbs of sodium hypochlorite were added to the mixture.An additional 19.5 lbs of sodium hydroxide (25% solution) were added,bringing the pH up to 13.3. The mixture was heated at about 80° C.closed lid for about 1 hour and then cooled to a temperature of 17° C.The mixture was then transferred to an ultrafiltration feed tank. About0.5 L of 6.3% hydrochloric acid was added to the mixture in the feedtank to bring the pH down to about 7.8. The ultrafiltration wascompleted in about 13 hours when the desired salt levels andconcentration were achieved. The solution was then filtered at 15.6%solids through 1.0 GF and 0.45 μGF filters and diluted to 41.3 lbs for asolids content of 14.8%. Finally, 3 lbs deionized water and 55.8 g ofProxel GXL (available from Arch Chemicals, Smyrna, Ga. and Avecia,Billingham, UK) were added to the mixture.

The resulting dispersion had a solids content of 14.9%, a surfacetension of 69 dynes/cm, a pH of 8.1, a conductivity of 1.45 mS and aviscosity of 3.0 cP. The changes in viscosity, pH and surface tension ofthe dispersion stored at 70° C. for three weeks are summarized below.

Viscosity (cP) pH Surface Tension (dynes/cm) Original 3.0 8.1 69 Week 1@ 70° C. 2.49 7.4 70.8 Week 2 @ 70° C. 2.45 7.3 71.8 Week 3 @ 70° C.2.59 7.3 70.7

An analysis of the components in the dispersion showed 14 ppm Cl, 151ppm SO₄, 4.2 ppm Ca, 4.8 ppm Fe, 1.8 ppm Mg and 5035 ppm Na. The averageparticle size was 119.3 nm.

Example 4 Black Pigment Dispersion Sulfonation/Oxidation of a FurnaceCarbon Black with Primary Particle Size of 16 nm with Milling

The procedure of Example 2 was repeated using 40 g of furnace carbonblack (available from Cabot Corporation, Billerica, Mass.), with aprimary particle size of 16 nm and a CTAB surface area of 255 m²/g. Thecarbon black was sulfonated with a 1:1 mixture of commercial grade(93-98%) sulfuric acid (200 g) and 20% oleum (209 g) at 120° C. for aminimum of 18 hours. The oxidation with sodium hypochlorite (˜8%solution, 406 g) took place using the mill described in Example 1, andwas then driven to completion by heating to 80° C. with good mixing, forone hour. The product of the reaction was worked up as detailed inExample 1. The carbon dispersion so obtained was filtered through a 0.7micron GF filter disk and was found to be a stable dispersion at roomtemperature.

The resulting dispersion had a solids content of 11.3% solids and a pHof 8.42. An analysis of the components in the dispersion showed 11 ppmCl, 173 ppm SO₄, 2.6 ppm Ca, 16 ppm Fe and 5320 ppm Na. The averageparticle size was 129 nm.

Example 5 Black Pigment Dispersion Sulfonation/Oxidation of a FurnaceCarbon Black with Primary Particle Size of 13 nm, with Milling

Example 4 was repeated using 40 g of furnace carbon black (availablefrom Columbian Chemicals, Marietta, Ga.) with a primary particle size of13 nm and CTAB surface area of 206 m²/g.

The resulting dispersion had a solids content of 12.1% solids and a pHof 7.8. An analysis of the components in the dispersion showed 10 ppmCl, 72 ppm SO₄, 2.8 ppm Ca, 17 ppm Fe and 4349 ppm Na. The averageparticle size was 89.1 nm.

Example 6 Black Pigment Dispersion Sulfonation/Oxidation with IncreasedSurface Acidic Groups

The procedure of Example 3 was repeated except that a second oxidationstep was performed before purification by adding additional sodiumhydroxide in an amount equivalent to that added in the first oxidationstep. In this instance after the second stage oxidation the mixture washeated at 80° C., and the temperature and pH of the mixture weremaintained at 80° C. and greater than 9.0, respectively, for a total of48 hours.

The resulting dispersion had a solids content of 10.56% solids, asurface tension of 68.7 dynes/cm, a viscosity of 1.92 cP, and aconductivity of 1.23 mS. An analysis of the components in the dispersionshowed 10 ppm Cl, 56 ppm SO₄, 9.9 ppm Ca, 6.4 ppm Fe, 1.0 ppm Mg, and4330 ppm Na. The average particle size was 106.8 nm.

Example 7 Black Pigment Dispersion Sulfonation/Oxidation andPurification at Elevated Temperature

Example 6 was repeated using the two step oxidation, each step beingcarried out at 80° C. for a one hour period. After the second oxidationand heat period the reaction mixture was cooled to 60° C. and purifiedby ultrafiltration. The ultrafiltration was run at a temperature of50-60° C. until the chloride and sulfate content of the feed sample wasless than 100 ppm. The product was then concentrated to 14.1% solids andmixed with 0.3% wt/wt Proxel GXL (available from Arch Chemicals, Smyrna,Ga.). Finally, the product was filtered through a 0.7 micron GF filter.

The resulting dispersion had a solids content of 14.1%, a pH of 7.6, asurface tension of 68.8 dynes/cm, a conductivity of 1.20 mS, and aviscosity of 2.45 cP. The changes in viscosity, pH and surface tensionof the dispersion stored at 70° C. for three weeks are summarized below.

Viscosity (cP) pH Surface Tension (dynes/cm) Original 2.45 7.6 68.8 Week1 @ 70° C. 2.53 7.2 70.5 Week 2 @ 70° C. 2.68 7.2 71.2 Week 3 @ 70° C.2.83 7.3 70.3

An analysis of the components in the mixture showed 20 ppm Cl, 33 ppmSO₄, 8.4 ppm Ca, 12.5 ppm Fe, 4875 ppm Na, and 2584 ppm sulfur. Theparticle size of the dispersion was 119 nm.

Example 8 Black Pigment Dispersion Sulfonation/Oxidation with Millingand Purification at Elevated Temperature

The sulfonation cake from Example 3 (676.4 g) was re-dispersed indeionized water to a volume of ˜1800 ml. To this slurry was added NaOHto reach a pH of >10.5. The cake slurry was then milled using a mediamill (Hockmeyer Basket Mill) charged with 0.4 mm YTZ® beads (availablefrom Quackenbush Co., Inc., Crystal Lake, Ill.) for 2 hours. During themilling process the volume increased to ˜3500 ml with added deionizedwater. After the two hour milling period, the dispersion was split inhalf for the oxidation. Each half of the dispersion was oxidized with954 g of sodium hypochlorite (10% solution). The pH of each wasmaintained above 9.0 with the addition of sodium hydroxide (25%solution). The dispersions were then heated at 80° C. for one hour thencooled to 35° C. After cooling, a second portion of sodium hypochlorite(954 g at 10%) was added to each dispersion. Again, the pH was keptabove 9.0 with the addition of sodium hydroxide. The dispersions werethen heated to 80° C. for an additional hour.

This process was repeated a total of 3 times to gain a larger amount ofproduct. All of the oxidized products (6 total) were combined forultrafiltration. The dissolved impurities were removed byultrafiltration until each of the chloride content and the sulfatecontent of the feed sample is less than 100 ppm. The dispersion wastaken and then heated to 80° C. overnight. After the overnight stirperiod the dispersion was again purified by ultrafiltration to removethe salts. The dispersion was again heated overnight at a temperature of80° C. After the second heat step the dispersion was purified byultrafiltration running at a elevated temperature of 50-60° C. untileach of the chloride content and the salt content of the feed sample wasless than 50 ppm. The product was then concentrated to 15.9% solids andmixed with 0.3% wt/wt Proxel GXL (available from Arch Chemicals, Smyrna,Ga.). Finally, the product was filtered through a 0.3 micron depthpolypropylene filter (available from Ball Corporation, Port Washington,N.Y.).

The resulting dispersion had a solids content of 15.91% solids, a pH of8.5, a surface tension of 70.5 dynes/cm, a viscosity of 2.65 cP, and aconductivity of 1.22 mS. The changes in viscosity, pH and surfacetension of the dispersion stored at 70° C. for three weeks aresummarized below.

Viscosity (cP) pH Surface Tension (dynes/cm) Original 2.65 8.5 70.5 Week1 @ 70° C. 2.19 7.5 70.6 Week 2 @ 70° C. 1.94 7.6 67 Week 3 @ 70° C.2.11 7.5 71.0

An analysis of the components in the dispersion showed 4 ppm Cl, 7 ppmSO₄, 8.3 ppm Ca, 16.1 ppm Fe, 1.0 ppm Mg, and 5065 ppm Na. The averageparticle size was 97.8 nm.

Example 9 Black Pigment Dispersion Sulfonation/Oxidation with IncreasedSurface Acidic Groups and Particle Size Reduction with Milling

Example 6 was repeated except that a mill (Hockmeyer Basket Mill)charged with 0.4 mm YTZ® beads (available from Quackenbush Co., Inc.,Crystal Lake, Ill.) was used during the first oxidation step with thesulfonation cake.

The resulting dispersion had a solids content of 16.9%, a surfacetension of 69.9 dynes/cm, a conductivity of 1.53 mS and a viscosity of3.0 cP. An analysis of the components in the dispersion showed 12 ppmCl, 65 ppm SO₄, 7.8 ppm Ca, 0.6 ppm Mg, 9.7 ppm Fe and 6096 ppm Na. Theaverage particle size was 98.1 nm.

Example 10 Magenta Pigment Dispersion Sulfonation/Oxidation of CIPigment Red 122

80 g of commercial pigment red 122 (available from Lansco Colors,Montvale, N.J.) were sulfonated with 95% sulfuric acid (394 g) at 60° C.for 20 minutes. The reaction mixture was cooled to 41° C. and quenchedin water and ice. The final quench temperature was 0° C. Theprecipitated product was isolated by filtration and washed free ofdissolved material. A part (55 g, 14.3%) of the product cake wasoxidized in the lab using a media mill (Hockmeyer Mill) charged with 0.4mm YTZ® beads (available from Quackenbush Co., Inc., Crystal Lake, Ill.)at 2800 rpm, with sodium hypochlorite (commercial grade, 12% solution,56 g diluted to 120 g with deionized water). The pH was maintained above10 with the addition of 2.92 g calcium free sodium hydroxide (25%solution). After three hours, additional sodium hypochlorite (20 gdiluted to 55 g, as before) was added and milled for an additional 135minutes. The dissolved impurities were removed by ultrafiltration untileach of the chloride content and the sulfate content of the feed samplewas less than 50 ppm. The product was then concentrated to 4.8% solidsand mixed with 0.3%, wt/wt Proxel GXL (available from Arch Chemicals,Smyrna, Ga.). Finally the product was filtered through 0.7 micron GFfilter.

The resulting dispersion had a solids content of 4.8% and a viscosity of1.34 cP. An analysis of the components in the dispersion showed 82 ppmCl, 538 ppm SO₄, 10.0 ppm Ca, 3.5 ppm Mg, 8.2 ppm Fe and 539 ppm Na.

Example 11 Magenta Pigment Dispersion Sulfonation/Oxidation of CIPigment Red 122)

60 g of commercial pigment red 122 (available from Lansco Colors,Montvale, N.J.) were sulfonated with 90% sulfuric acid (525 g) at 80° C.for 5 hours. The reaction mixture was quenched in water and ice. Thefinal quench temperature was 0° C. The precipitated product was isolatedby filtration and washed free of dissolved material. The product cakewas slurried in deionized water and oxidized in the lab using a mediamill (Hockmeyer Mill) charged with 0.4 mm YTZ® beads (available fromQuackenbush Co., Inc., Crystal Lake, Ill.) at 2800 rpm, with 240 gsodium hypochlorite (commercial grade, 12% solution). The pH wasmaintained above 9 with the addition of 2.97 g calcium free sodiumhydroxide, 25% solution. After three hours, 10.36 g of additional sodiumhydroxide was added and milled for an additional 2 hours. The dissolvedimpurities were removed by ultrafiltration until each of the chloridecontent and the sulfate content of the feed sample was less than 10 ppm.The product was then concentrated to 11% solids and mixed with 0.3%,wt/wt Proxel GXL (available from Arch Chemicals, Smyrna, Ga.). Finally,the product was filtered through a 0.7 micron GF filter.

The resulting dispersion had a solids content of 11.70% and a viscosityof 2.88 cPs. An analysis of the components in the dispersion showed 9ppm Cl, 6 ppm SO₄, 4.1 ppm Ca, 1.2 ppm Mg, 2.7 ppm Fe, 179 ppm S and 568ppm Na. The dispersion pH was 8.51.

Example 12 Magenta Pigment Dispersion Sulfonation/Oxidation of CIPigment Red 122)

60 g of commercial pigment red 122 (available from BASF Colors,Charlotte, N.C.) were sulfonated with 90% sulfuric acid (524 g) at 80°C. for 5 hours. The reaction mixture was quenched in water and ice. Thefinal quench temperature was 0° C. The precipitated product was isolatedby filtration and washed free of dissolved material. The product cakewas slurried in deionized water and oxidized in the lab using a mediamill (Hockmeyer Mill) charged with 0.4 mm YTZ® beads (available fromQuackenbush Co., Inc., Crystal Lake, Ill.) at 2800 rpm, with 350 gsodium hypochlorite (commercial grade, 12% solution). The pH wasmaintained above 9 with the addition of 2.9 g calcium free sodiumhydroxide, 25% solution. After three hours, 14.9 g of additional sodiumhydroxide were added and milled for additional 2 hours. The dissolvedimpurities were removed by ultrafiltration until each of the chloridecontent and the sulfate content of the feed sample was less than 10 ppm.The product was then concentrated to 10% solids and mixed with 0.3%,wt/wt Proxel GXL (available from Arch Chemicals, Smyrna, Ga.). Finally,the product was filtered through a 0.7 micron GF filter.

The resulting dispersion had a solids content of 9.81% and a viscosityof 2.01 cPs. An analysis of the components in the dispersion showed 16ppm Cl, 7 ppm SO₄, 3.2 ppm Ca, 1 ppm Mg, 1 ppm Fe, 239 ppm S and 605 ppmNa. The dispersion pH was 8.19.

Example 13 Magenta Pigment Dispersion Sulfonation/Oxidation of CIPigment Red 122

60 g of commercial pigment red 122 (available from Clariant Colors,Charlotte, N.C.) were sulfonated with 90% sulfuric acid (475 g) at 80°C. for 5 hours. The reaction mixture was quenched in water and ice. Thefinal quench temperature was 0° C. The precipitated product was isolatedby filtration and washed free of dissolved material. The product cakewas slurried in deionized water and oxidized in the lab using a mediamill (Hockmeyer Basket Mill) charged with 0.4 mm YTZ® beads (availablefrom Quackenbush Co., Inc., Crystal Lake, Ill.) at 2800 rpm, with 350 gsodium hypochlorite (commercial grade, 12% solution). The pH wasmaintained above 9 with the addition of 2.6 g calcium free sodiumhydroxide, 25% solution. After three hours, 12.6 g of additional sodiumhydroxide were added and milled for additional 2 hours. The dissolvedimpurities were removed by ultrafiltration until each of the chlorideand sulfate content of the feed sample was less than 10 ppm. The productwas then concentrated to 11% solids and mixed with 0.3%, wt/wt ProxelGXL (available from Arch Chemicals, Smyrna, Ga.). Finally, the productwas filtered through 0.7 micron GF filter.

The resulting dispersion had a solids content of 11.07% and a viscosityof 2.1 cP. An analysis of the components in the dispersion showed 7 ppmCl, 5 ppm SO₄, 3.4 ppm Ca, 0.9 ppm Mg, 1.2 ppm Fe, 133 ppm S and 777 ppmNa. The dispersion pH was 8.09. The introduction of S (0.344 mMoles of Sper gram of sample) via sulfonation was confirmed by elemental analysisof a dried sample (by Schwarskopf Microanalytical Laboratory, Woodside,N.Y.).

Example 14 Magenta Pigment Dispersion Sulfonation/Oxidation of CIPigment Red 122

60 g of commercial pigment red 122 (available from Sun Chemical,Cincinnati, Ohio) were sulfonated with 90% sulfuric acid (525 g) at 80°C. for 5 hours. The reaction mixture was quenched in water and ice. Thefinal quench temperature was 0° C. The precipitated product was isolatedby filtration and washed free of dissolved material. The product cakewas slurried in deionized water and oxidized in the lab using a mediamill (Hockmeyer Basket Mill) charged with 0.4 mm YTZ® beads (availablefrom Quackenbush Co., Inc., Crystal Lake, Ill.) at 2800 rpm, with 280 gsodium hypochlorite (commercial grade, 12% solution). The pH wasmaintained above 9 with the addition of 1.78 g calcium free sodiumhydroxide, 25% solution. After three hours, 10 g of additional sodiumhydroxide were added and milled for an additional 2 hours. The dissolvedimpurities were removed by ultrafiltration until each of the chloridecontent and the sulfate content of the feed sample was less than 10 ppm.The product was then concentrated to 11% solids and mixed with 0.3%,wt/wt Proxel GXL (available from Arch Chemicals, Smyrna, Ga.). Finally,the product was filtered through 0.7 micron GF filter.

The resulting dispersion had a solids content of 11.70% and a viscosityof 2.88 cP. An analysis of the components in the dispersion showed 9 ppmCl, 5 ppm SO₄, 1.8 ppm Ca, 0.4 ppm Mg, 0.6 ppm Fe, 71.3 ppm S and 460ppm Na. The dispersion pH was 8.75

Comparative Example 1 Magenta Pigment Dispersion Oxidation of CI PigmentRed 122 as Disclosed in U.S. Pat. No. 6,596,068

25 g of commercial pigment red 122 (available from Lansco Colors,Montvale, N.J.) were added to 500 ml deionized water and mixed at 1000rpm to wet the pigment. Then the mixture was milled for 1.5 hours usinga media mill (Hockmeyer Mill) charged with 0.4 mm YTZ® beads (availablefrom Quackenbush Co., Inc., Crystal Lake, Ill.) at 3000 rpm. Milling wascontinued for another hour after adding sodium hypochlorite (125 g,commercial grade, 10% solution). The milled product was stirredovernight and then isolated as a wet cake. The dissolved impurities wereremoved first by washing the cake with deionized water and then byultrafiltration until each of the chloride content and the sulfatecontent of the feed sample was less than 50 ppm. The product was thenconcentrated to 7.74% solids and mixed with 0.3%, wt/wt Proxel GXL(available from Arch Chemicals, Smyrna, Ga.). The product was not astable dispersion, settling was noticed on standing three days atambient temperature.

The resulting dispersion had a solids content of 7.74% solids, a surfacetension of 70.9, a viscosity of 1.91 cP, and a conductivity of 0.980 mS.An analysis of the components in the dispersion showed 57 ppm Cl, 474ppm SO₄, 24 ppm Ca, 2.3 ppm Mg, 8.3 ppm Fe and 335.7 ppm Na.

Comparative Example 2 Magenta Pigment Dispersion Sulfonation of CIPigment Red 122 as Disclosed in U.S. Pat. No. 6,648,954

20 g of commercial pigment red 122 (available from Lansco Colors,Montvale, N.J.) were added to 95% sulfuric acid (200 g) and heated to80° C. After 2 hours at 80° C., it was quenched into an ice/watermixture. The isolated wet cake was washed with deionized water to removeexcess acid and then re-dispersed in 200 g deionized water. A sufficientamount of calcium free sodium hydroxide was added to bring the pH toabout 10. The dissolved impurities were removed by ultrafiltration untileach of the chloride content and the sulfate content of the feed samplewas less than 50 ppm. The product was then concentrated to 7.35% solidsand mixed with 0.3%, wt/wt Proxel GXL (available from Arch Chemicals,Smyrna, Ga.). The product could not be filtered through 0.7 micron GFfilter. After 1 week in an oven at 70° C., the material showed hardsettling in the bottom of the container.

The resulting dispersion had a solids content of 7.35%, a surfacetension of 70.5 dynes/cm, a viscosity of 2.27 cP, and a conductivity of0.39 mS. An analysis of the components in the dispersion showed 10 ppmCl, 50 ppm SO₄, 0.9 ppm Ca, 3.9 ppm Fe, 0.2 ppm Mg and 324.7 ppm Na.

Example 15 Cyan Pigment Dispersion Example of Sulfonation/Oxidation withCI Pigment Blue 15:1

80 g of commercial pigment blue 15:1 (available from Fanwood Chemical,Fanwood, N.J.) were sulfonated with 99.5% sulfuric acid (424 g) at114-120° C. for 160 minutes. The reaction mixture was cooled to 100° C.and quenched in water and ice. The final quench temperature was 25° C.The precipitated product was isolated by filtration and washed free ofdissolved material. A part (160 g, 48%) of the product cake wasdispersed in the lab using a media mill (Hockmeyer Baske Mill) chargedwith 0.4 mm YTZ® beads (available from Quackenbush Co., Inc., CrystalLake, Ill.) at 2800 rpm. The pH was maintained above 10 with theaddition of 47.4 g calcium free sodium hydroxide, 25% solution. Afterthree and a half hours, one half of this dispersion was oxidized withsodium hypochlorite (commercial grade, 12% solution, 56 g diluted to 126g with deionized water) in the mill for additional hour. The dissolvedimpurities were removed by ultrafiltration until each of the chloridecontent and the sulfate content of the feed sample was less than 50 ppm.The product was then concentrated to 4.8% solids and mixed with 0.3%wt/wt Proxel GXL (available from Arch Chemicals, Smyrna, Ga.). Finally,the product was filtered through 0.7 micron GF filter.

The resulting dispersion had a solids content of 4.8% and a viscosity of1.34 cP. An analysis of the components in the dispersion showed 82 ppmCl, 538 ppm SO₄, 10.0 ppm Ca, 3.5 ppm Mg, 8.2 ppm Fe and 539 ppm Na.

Example 16 Cyan Pigment Dispersion Example of Sulfonation/Oxidation withCI Pigment Blue 15:3

120 g of commercial pigment blue 15:3 (available from BASF Corporation,Charlotte, N.C.) were sulfonated with a mixture of 300 g of sulfuricacid (95%) and 300 g of 20% oleum at 120° C. for 6 hours. The reactionmixture was cooled to 100° C. and quenched in water and ice. The solidproduct was isolated by filtration and washed free of dissolvedmaterial. The cake was dispersed using a media mill (Hockmeyer BasketMill) charged with 0.4 mm YTZ beads (available from Quackenbush Co.Inc., Crystal Lake, Ill.) at 3000 rpm. The pH was maintained above 9.0with the addition of 60 g calcium free sodium hydroxide, 25% solution.After 2 hours on the mill the dispersion was oxidized with 371.6 g ofsodium hypochlorite (10.9%) in the mill for an additional 3 hours. Theresulting product was then heated to 80° C. for a period of 1 hour. Thedissolved impurities were then removed by ultrafiltration until each ofthe chloride content and the sulfate content of the feed sample was lessthan 100 ppm. The product was concentrated to 7.7% solids and mixed with0.3% wt/wt Proxel GXL (available from Arch Chemicals, Smyrna, Ga.).Finally, the product was filtered through a 0.7 micron GF filter.

The resulting dispersion had a solids content of 7.73% solids and a pHof 8.24. An analysis of the components in the dispersion showed 23 ppmCl, 21 ppm SO₄, 1.7 ppm Ca, 1.5 ppm Fe, 1830 ppm Na and 1560 ppm sulfur.The dispersion also had a viscosity of 2.10 cP, a surface tension of69.1 dynes/cm, and a conductivity of 2.4 mS. The introduction of S(0.894 mMoles of S per gram of sample) via sulfonation was confirmed byelemental analysis of a dried sample (by Schwarskopf MicroanalyticalLaboratory, Woodside, N.Y.).

Example 17 Cyan Pigment Dispersion Example of Sulfonation/Oxidation withCI Pigment Blue 15:3

40 g of commercial pigment blue 15:3 (available from BASF Corporation,Charlotte, N.C.) were sulfonated with 200 g sulfuric acid (95%) at 120°C. for 24 hours. The reaction mixture was cooled to 100° C. and quenchedin water and ice. The solid product was isolated by filtration andwashed free of dissolved material. The acidic cake was brought to a pHof 8.0 and re-dispersed in deionized water. The resulting mixture wasfiltered to isolate the cake. The cake was dispersed using a media mill(Hockmeyer Basket Mill) charged with 0.4 mm YTZ beads (available fromQuackenbush Co. Inc., Crystal Lake, Ill.) at 3000 rpm. After 2 hours onthe mill the dispersion was oxidized with 55 g of 10.9% sodiumhypochlorite in the mill for an additional 2 hours. The resultingproduct was then heated to 65° C. for 1 hour. The dissolved impuritieswere removed by ultrafiltration until each of the chloride content andthe sulfate content of the feed sample was less than 100 ppm. Theproduct was concentrated to 7% solids and mixed with 0.3% wt/wt ProxelGXL (available from Arch Chemicals, Smyrna, Ga.). Finally, the productwas filtered through a 9-0.8 micron depth GF filter.

The resulting dispersion had a solids content of 6.38% and a pH of 7.5.An analysis of the components in the dispersion showed 160 ppm Cl, 21ppm SO₄, 2.7 ppm Ca, 2.9 ppm Fe, 713 ppm Na and 1529 ppm sulfur. Thedispersion also had a viscosity of 6.9 cP, a surface tension of 68.8dynes/cm, and a conductivity of 1.38 mS.

Example 18 Yellow Pigment Dispersion Example of Sulfonation/Oxidationwith Solvent Yellow 33

40 g of commercial solvent yellow 33 (available from Rainbow ChemicalsCo., Northbrook, Ill.) were sulfonated using 200 g sulfuric acid (95%)at 120° C. for 6 hours. The reaction mixture was cooled to 100° C. andquenched in ice and water. The solid product was isolated by filtrationand washed free of dissolved material. The resulting mixture wasfiltered to isolate the cake. The cake was dispersed using a media mill(Hockmeyer Basket Mill) charged with 0.4 mm YTZ beads (available fromQuackenbush Co. Inc., Crystal Lake, Ill.) at 3000 rpm. After 3 and ahalf hours on the mill, the dispersion was oxidized with 65 g of 10.9%sodium hypochlorite in the mill for an additional hour. The resultingproduct was then heated to 60° C. for one hour. The dissolved impuritieswere removed by ultrafiltration until each of the chloride content andthe sulfate content of the feed sample was less than 100 ppm. Theproduct was concentrated to 2.17% solids and mixed with 0.3% wt/wtProxel GXL (available from Arch Chemicals, Smyrna, Ga.). Finally, theproduct was filtered through a 9-0.8 micron depth GF filter.

The resulting dispersion had a solids content of 2.17% and a pH of 6.99.An analysis of the components in the dispersion showed 4 ppm Cl, 68 ppmSO₄, 2.3 ppm Ca, 15.2 ppm Fe, 187 ppm Na and 278 ppm sulfur. Thedispersion had a viscosity of 1.55 Cp, a surface tension of 57.7dynes/cm, and a conductivity of 0.578 mS.

Example 19 Replacing Counterions Associated with Surface ModifyingGroups

Counterions associated with surface modifying groups of a pigment may besubstituted with other suitable cations as exemplified by the followingprocedure.

The dispersion obtained from Example 3 (3200 g, 14.85% solids, pH=8.1)was further purified by ultrafiltration while the pH of the product wasadjusted slowly downward with dilute hydrochloric acid (1 pH unit at atime over several hours) without shocking the pigment dispersion. Atotal of 34.7 g of 25% HCl was used to lower the pH to 5.5. When theproduct was found to be free of dissolved impurities, it wasconcentrated to 2693.1 g (14% solids, 12 ppm Cl and 45 ppm SO₄).

Different mixed salts (˜50% sodium) with monoethanolammonium (MEA),triethanolammonium (TEA), tetramethylammonium (TMA), tetrabutylammonium(TBA), lithium, potassium, and ammonium were formed in 300 g portions byadjusting the pH to about 8.0 with corresponding base (e.g., KOH, NH₄OH,etc.). The properties of the resulting dispersions are summarized inTable 1.

TABLE 1 Mixed salts with ~50% sodium ion content. Na⁺ K⁺ Li⁺ NH₄ ⁺ MEATEA TBA TMA Solids [%] 14.9 15.5 14.9 15.5 15.5 16.5 16.5 15.7 pH 7.98.4 8.5 8.5 8.4 8.4 8 8.6 Conductivity 1450 1375 1118 1305 1171 973 18601379 Surface Tension 69 53.5 64.7 69.5 61.1 59.4 59.2 55.4 Viscosity2.68 2.98 3.02 3.18 3.02 3.06 3.01 3.02 Na⁺ [ppm] 5035 3385 3489 34125213 3885 2919 3950 S [ppm] 2558 2950 2893 3631 3030 3236 1904 3189

Mixed salts (<20% sodium) were prepared in a similar manner to the mixedsalts (˜50% sodium) except that the pH was adjusted downward with dilutehydrochloric acid to a stable pH of 2.0 without shocking. The propertiesof the resulting dispersions are summarized in Table 2.

TABLE 2 Mixed salts with < 25% sodium ion content. Na⁺ K⁺ Li⁺ NH₄ ⁺ MEATEA TBA TMA Solids [%] 13.7 15.3 14.5 14.9 15.6 16.3 16.1 16.0 pH 7.77.1 7.3 7.1 6.8 8.1 7.1 7.6 Conductivity 2830 3050 2060 3090 2170 29601808 2960 Surface Tension 55 65 65 69.3 57.4 64.2 58.7 61.9 Viscosity2.77 3.19 3.11 3.24 3.38 3.33 3.36 3.44 Na⁺ [ppm] 5291 1110 1119 10891087 1017 934 1154 S [ppm] 2810 2611 2446 2507 2714 2465 2667 2689

Example 20 X-Ray Photoelectron Spectroscopy (XPS) Analyses

XPS data were collected and analyzed for Samples 1-4 (Table 3).

TABLE 3 XPS samples. Sample Sample Source 1 Carbon Black Gas carbonblack, available from Degussa, Akron, OH. 2 Carboxy Modified Sensijet ®Black SDP 1000 Carbon Black (available from Sensient Colors, Inc., St.Louis, MO). 3 Sulfonated Carbon Black Sulfonation cake from Example 3(washed and dried). 4 Sulfonated, Carboxy Modified pigment obtainedModified Carbon Black in Example 7.

The XPS data were acquired by EAG Labs (in Chanhassen, Minn.) using aPhysical Electronics Quantum 2000 Scanning XPS instrument with a probebeam of focused, monochromatic Al K_(α) 1486.6 eV radiation. Analyseswere conducted in a 1.5 mm×0.3 mm analysis area with a 45° correctionangle and no charge correction or charge neutralization. The x-raysgenerated photoelectrons that were energy analyzed and counted to revealthe atomic composition and chemistry of the sample surfaces. The escapedepth of the photoelectrons limited the depth of analysis to the outer˜50 Å. FIG. 1 provides a low resolution survey scan ranging from 0 to1100 eV binding energy. FIGS. 2-4 are high resolution spectra fromselected elements, which provide chemical state information.

Samples 1 and 3 were mounted directly in powder form. Samples 2 and 4(dispersed liquids) were prepared by drying down a small amount of theliquid under a nitrogen atmosphere and then grinding the resultant filmsto powders.

Elements detected on all samples included C, O, S and Cl. Samples 2 and4 also had Na present. A trace of organic N was present on Sample 4.

As shown in FIG. 2, the C 1s spectra of all samples were consistent witha dominant carbon black contribution that included a main, asymmetricC—C,H peak at about 284.5 eV, and a strong satellite due to unsaturatedbonds. Samples 2 and 4, both having been carboxy modified, also have astrong C 1s component at ˜288.3 eV binding energy, consistent with COONabonding. Although organic Cl was detected for all samples, the low levelof Cl present precludes observation of a C—Cl bond peak in the C 1sspectra. The same is true for potential C to S bonds and C to N bondsdue to the low concentrations of those elements. No attempt has beenmade to curve fit the C 1s peaks since the error associated with fittingthe basic amorphous carbon line shape is similar in intensity to most ofthe expected carbon functionalities (other than the clear COONa peak).

As shown in FIG. 3, the 0 is spectra of all samples had two componentsat roughly 531 and 533 eV, consistent with C═O and C-0 bonding. The C-0peak would include species such as hydroxyls, ethers and carboxylic acidgroups. The C═O peak would include ketone, ester, acrylate, andcarboxylic acid groups. Sulfone or sulfate oxygen contributions wouldboth overlap the C═O contribution, as would COONa contributions. Anapparent third component at ˜535 eV binding energy was actually due toan overlapping Na KLL feature present for Samples 2 and 4. Thiscomponent was removed from the spectra by subtraction of a referenceNaCl Na KLL spectrum for calculation of atomic concentration, and bycurve fitting for chemical state analysis.

Nitrogen was only detected at low level on sample 4 and no highresolution spectrum was acquired. Its binding energy in the surveyspectrum suggests an organic form.

As shown in FIG. 4, sulfur was present on all samples in at least twoforms. A reduced form, referred to in the spectral plots as sulfide, andan oxidized form, referred to in the plots as SOx (sulfate/sulfone).There was no spectral evidence to separate potential sulfate and sulfonecontributions. The sulfide peak intensity was similar for all foursamples, while the sulfate/sulfone peak intensity varied dramatically.The sulfide contributions, in some cases, required two components toobtain good curve fits. The nature of the multiple sulfide components isnot understood, but could be due to the presence of different sulfideforms, or could conceivably reflect a complex peak shape due tophotoelectron energy loss mechanisms within the carbon black matrix.Apparently the sulfide species are quite stable and not affected byeither the carboxy modification or sulfonation process as similaramounts of sulfide sulfur are observed on all samples. No evidence forany oxidized sulfur (SOx) is observed on the carboxy modified carbonblack sample. The only samples showing oxidized sulfur (SOx) are thesulfonated carbon black sample and the sulfonated, carboxy modifiedcarbon black sample.

The high resolution spectra were used to obtain surface composition byintegrating the areas under the photoelectron peaks and applyingempirical sensitivity factors. The Atomic % (Table 4), % of ElementsDetected (Table 5) and Atomic % by Chemical State (Table 6) for eachsample are presented below.

TABLE 4 XPS Surface Concentrations (Atomic %).¹⁻³ Sample C N O Na S Cl 1Carbon black 97.5 — 2.4 — 0.11 0.03 2 Carboxy modified 81.4 — 13.0 5.30.11 0.19 carbon black 3 Sulfonated carbon 94.0 — 5.4 — 0.58 0.03 black4 Sulfonated, carboxy 82.3 0.15 12.6 4.6 0.35 0.12 modified carbon black¹Normalized to 100% of the elements detected. XPS does not detect H orHe. ²Detection limits are typically between 0.05% and 1.0% for otherelements. ³A dash “—” indicates the element was not detected.

TABLE 5 Curve Fit Summary Table (% of Element Detected). %O as C═O, % Clas % Cl as % S as sulfate, metal organic % S as sulfate, sulfone, % O asSample chloride chloride sulfide sulfone COONa C—O 1 0 100 74 26 31 69 258 42 73 27 65 35 3 0 100 9 91 55 45 4 63 37 25 75 66 34

TABLE 6 Combined Table (Atomic % by Chemical State). O as C═O, sulfate,S as Cl as Cl as sulfone, S as sulfate, organic metal Sample C N COONa,O as C—O Na sulfide sulfone chloride chloride 1 97.5 — 0.7 1.6 — 0.080.03 0.03 0.00 2 81.4 — 8.5 4.5 5.3 0.08 0.03 0.08 0.11 3 94.0 — 2.9 2.4— 0.05 0.53 0.03 0.00 4 82.3 0.15 8.3 4.3 4.6 0.09 0.26 0.04 0.08

Example 21 Scanning Electron Microscopy (SEM) Analyses

SEM analyses were performed on base carbon black (Sample 1, Table 3),carboxy modified carbon black (oxidized) (Sample 2, Table 3) andsulfonated, carboxy modified carbon black (Sample 4, Table 3) using aHitachi S-4500 Field Emission Scanning Electron Microscope. The sampleswere dried at room temperature prior to analysis.

The SEM Images (15.0 kV×500 K 60 nm) of (a) carbon black with an averagediameter of ˜39.3±3 nm, (b) carboxy modified carbon black with anaverage diameter of ˜31.1±3 nm, and (c) sulfonated carboxy modifiedcarbon black with an average diameter of ˜38.7±2 nm, are provided inFIG. 5. The sizes were determined by pixelizing the image andidentifying boundaries using contrast. As shown in FIG. 5( a), there isno appreciable change in gross morphology of the base carbon black, aswould be expected with any surface modification.

Example 22 TGA Analysis

TGA was performed on TA Instruments' TGA instrument under nitrogenatmosphere, heating from 30° C. to 800° C. at a rate of 10° C. perminute. As shown in FIG. 6, the base carbon black (Sample 1, Table 3)had a gradual weight loss until 550° C. and then a much rapid weightloss. In comparison, the carboxy modified carbon black (Sample 2, Table3) and sulfonated, carboxy modified carbon black (Sample 4, Table 3) hadmore pronounced but gradual weight loss until about 700° C. A rapidweight loss at 780° C. for the carboxy modified carbon black as comparedto the more pronounced weight loss at 700° C. for the sulfonated,carboxy modified carbon black differentiates the two types of surfacemodifications. There was a slight shift in the slope (rate of weightloss) at about 300° C. for both modified carbon blacks. The gradualweight loss in the range of 100-700° C. is attributable to loss ofsurface groups such as carboxyl and lactone. The marked weight lossabove 700° C. as noted in the case of sulfonated carboxy modified carbonblack is attributed to the loss of SO₃ surface group.

Each of the modified carbon blacks exhibit three distinct weight lossregions. It is possible to calculate the weight loss over these regionsas equivalent to CO₂ gas released. As shown in FIG. 7 and as summarizedin Table 7, the sulfonated, carboxy modified carbon black exhibits aweight loss equivalent to 1424 μMoles CO₂ per gram of pigment from103-313° C., a weight loss equivalent to 806 μMoles CO₂ per gram ofpigment from 313-463° C., and a weight loss equivalent from 1751 μMolesCO₂ per gram of pigment from 463-773° C.

TABLE 7 Weight loss analysis for sulfonated, carboxy modified carbonblack in FIG. 7. Weight Per Moles μMoles Starting Weight = 41.891Difference Gram C CO₂ CO₂ Weight @ 103° C. = 39.865 0 0 0 0 Weight @313° C. = 37.24 2.625 0.06266 0.001424 1424 Weight @ 463° C. = 35.7551.485 0.03545 0.000806 806 Weight @ 773° C. = 32.527 3.228 0.077060.001751 1751

As shown in FIG. 8 and as summarized in Table 8, the carboxy modifiedcarbon black exhibits a weight loss equivalent to 1239 μMoles CO₂ pergram of pigment from 101-308° C., a weight loss equivalent to 782 μMolesCO₂ per gram of pigment from 308-441° C., and a weight loss equivalentfrom 964 μMoles CO₂ per gram of pigment from 441-651° C.

TABLE 8 Weight loss analysis for carboxy modified carbon black in FIG.8. Weight Per Moles μMoles Starting Weight = 19.443 Difference Gram CCO₂ CO₂ Weight @ 101° C. = 18.99 0 0 0 0 Weight @ 308° C. = 17.139 1.060.05452 0.001239 1239 Weight @ 441° C. = 16.47 0.669 0.03441 0.000782782 Weight @ 651° C. = 15.645 0.825 0.04243 0.000964 964

By comparison, as shown in FIG. 9 and as summarized in Table 9, carbonblack exhibits a weight loss equivalent to 165 μMoles CO₂ per gram ofpigment from 103-300° C. and a weight loss equivalent to 447 μMoles CO₂per gram of pigment from 300-660° C.

TABLE 9 Weight loss analysis for carbon black in FIG. 9. Weight PerMoles μMoles Starting Weight = 2.0243 Difference Gram C CO₂ CO₂ Weight @103° C. = 1.9952 0 0 0 0 Weight @ 300° C. = 1.9805 0.0147 0.007260.000165 165 Weight @ 660° C. = 1.9407 0.0398 0.01966 0.000447 447

Example 23 Surface Active Hydrogen Analysis

The samples (as aqueous dispersions) were titrated with undiluted 2.000N HCl from a 50 ml burette calibrated to 0.1 ml. The samples and thetitrant were not diluted so that the pH of 2.0 could be achieved using areasonable quantity of titrant, and so that the volume change over thecourse of the titration would be less (ca. 10% increase in volume duringthe course of the titration). Data are summarized in Table 10 for theacid uptake over the pH interval 10.2 to 2.0 for the carbon dispersionsand for deionized water. The first column shows the total uptake of HClin mMoles over this pH interval, and the second column shows the uptakeconverted to mMoles/g based upon the % solids. As expected, the uptakeper gram is largest for the product described in Example 7. Exampleswith oxidation and the carbon black raw material are included forcomparison.

TABLE 10 Bulk acidity by pH titration. mMoles (mMoles HCl)/ Sample ofHCl g Solid Water Blank 1.0 NA Carbon Black 1.4 0.2 Oxidized carbonblack 6.6 1.1 (Sensijet ® Black SDP 100 available from Sensient ColorsInc., St. Louis, MO) Oxidized carbon black 10.2 1.5 (Sensijet ® BlackSDP 1000 available from Sensient Colors Inc., St. Louis, MO) Example 19.9 1.4 Example 7 12.3 1.7

Example 24 Elemental Analysis

The surface modified carbon black dispersion (sulfonated, carboxymodified carbon black) made according to Examples 2 and 8 were analyzedas a dry powder (dried in the oven at 70° C. to constant weight) bySchwarskopf Microanalytical Laboratory, Woodside, N.Y. and compared withthe original carbon black powder and oven dried, thoroughly washedsulfonated acid cake. The surface modified pigment blue 15 (Example 16)and pigment red 122 (Example 13) were similarly analyzed as a drypowder. The results of the elemental analysis are summarized in Table11.

TABLE 11 Elemental analysis (% C, H, N, & S). Sample C H N S Na¹ 1Carbon black 91.35 1.15 0.10 0.32 — 2 Sulfonated carbon black 86.01 1.04<0.1 2.30 — 3 Sulfonated, carboxy modified 75.70 0.80 0.27 1.53 3.47carbon black (Example 8) 4 Sulfonated, carboxy modified 78.11 0.15 0.142.36 4.08 carbon black (Example 2) 5 Sulfonated carboxy modified 58.342.80 14.96 2.06 2.37 PB15 (Example 16) 6 Sulfonated carboxy modified71.58 4.28 7.90 0.11 0.70 PR122 (Example 13) ¹The sodium was calculated@100% solids from ICP metal analysis of the original dispersion.

The results of the elemental analysis indicate that Example 8 yields amodified carbon black with 0.478 mMoles of S and 1.51 mMoles of activehydrogen per gram of carbon.

The results of the elemental analysis indicate that Example 2 yields amodified carbon black with 0.738 mMoles of S and 1.77 mMoles of activehydrogen per gram of carbon.

The results of the elemental analysis indicate that Example 16 yields amodified pigment blue 15 with 0.894 mMoles of S and 1.03 mMoles ofactive hydrogen per gram of pigment.

The results of the elemental analysis indicate that Example 13 yields amodified pigment red 122 with 0.034 mMoles of S and 0.304 mMoles ofactive hydrogen per gram of pigment.

Ink Examples

In the following examples, the print performance characteristics of theinks were analyzed according to the aforementioned water resistanceprocedure, highlighter resistance procedure, rub resistance procedure,ImageXpert instrument procedure (line width, edge acuity, intercolorbleed, mottle), optical density procedure, L*a*b* color spacecoordinates procedure, cartridge start-up procedure, and lightresistance procedure.

Example 25

The following composition is an ink formulation incorporating theself-dispersing pigment made according to Example 7.

TABLE 12 Ink A formulation. Ingredients % (by Weight) Self-DispersingPigment 0.170-0.200 (Dispersion) made according to Example 72-Pyrrolidone, 95% 0.05 Diethylene Glycol 0.12 Non-Ionic Surfactant0.001-0.005 (PEG 600) Proxel GXL 0.003 IPA Anhydrous 0.010-0.020Deionized Water balance

The ink composition was formulated using a two vessel method. A firstvessel was used to make the ink base or diluent. A second vessel wasused to slowly dilute the pigmented dispersion during a process commonlycalled a “letdown.” The equipment used in the method of making the inkwas glass.

First, the water was added to the first vessel. A mixing device was thenplaced inside the vessel to agitate the water and provide mixing whilethe other ingredients are added. Mixing was achieved using a magneticstirring device. Next, 2-pyrrolidone, diethylene glycol, and IPAanhydrous were added to the vessel. These were allowed to dissolve.Then, PEG 600 and Proxel GXL were added and allowed to dissolve.

The second vessel was prepared by adding the pigment dispersion madeaccording to Example 7 to the vessel. A magnetic stirring device wasthen placed into the vessel. After all of the ingredients in the diluenthad dissolved, the dispersion and the diluent were mixed together. Afterthe diluent and dispersion were combined, the ink was mixed for about 1hour, or until it was homogenous. After mixing, the ink was filteredusing a 1 micron glass filter (available from Whatman, Kent, England).

Print Performance Testing

The print performance of the above-identified ink was compared to inkscomprising Sensijet® Black SDP 100 and 1000 available from SensientColors Inc. (St. Louis, Mo.). The comparison inks were prepared usingSensijet® Black SDP 100 and 1000 in the Ink A formulation. The carbonblack inks were printed on three commonly used copy papers—HewlettPackard Multipurpose Paper, Office Depot 104 paper, and Xerox 4200multipurpose paper. In the highlighter test two highlighters wereused—Sharpie Accent (H1) and Eberhard Faber 4009 (H2).

The analysis of the prints showed Ink A to be superior in all testscompared to the comparative inks containing Sensijet® Black SDP 100 and1000.

TABLE 13 Water Resistance. HP Office Multipurpose Depot 104 Xerox 4200Sensijet ® Black SDP 0.13 0.09 0.08 100 OD difference Sensijet ® BlackSDP 0.14 0.06 0.12 1000 OD difference Ink A 0.11 0.05 0.10 OD difference

TABLE 14 Highlighter Resistance (H1 = Sharpie Accent, H2 = EberhardFaber). HP Office Multipurpose Depot 104 Xerox 4200 Sensijet ® Black SDP100 0.6 0.31 0.62 OD difference (H1) Sensijet ® Black SDP 0.42 0.19 0.521000 OD difference (H1) Ink A 0.35 0.16 0.27 OD difference (H1)Sensijet ® Black SDP 100 0.45 0.28 0.47 OD difference (H2) Sensijet ®Black SDP 0.42 0.21 0.47 1000 OD difference (H2) Ink A 0.42 0.18 0.37 ODdifference (H2)

TABLE 15 Rub Resistance. HP Office Multipurpose Depot 104 Xerox 4200Sensijet ® Black SDP 0.12 0.06 0.10 100 OD difference Sensijet ® BlackSDP 0.12 0.04 0.08 1000 OD difference Ink A 0.09 0.03 0.05 OD difference

Example 26

The following are different salt forms of the black dispersion preparedaccording to Example 3, converted to a mixed salt containing <50% Nasalt, and incorporated into the following ink formulations using theprocedure described below.

TABLE 16 Inks B-H. Ink Ink Ink Ink Ink Ink Ink B C D E F G H Salt FormMEA K⁺ NH4⁺ TMA TEA Li⁺ Na⁺ Water, deionized (%) 50.6 50.6 50.6 50.952.2 49.6 51.7 Bioban (%) 0.1 0.1 0.1 0.1 0.1 0.1 0.1 2-pyrrolidone (%)5.0 5.0 5.0 5.0 5.0 5.0 5.0 PEG 400 (%) 13.0 13.0 13.0 13.0 13.0 13.013.0 Cobratec Solution (%) 0.3 0.3 0.3 0.3 0.3 0.3 0.3 (available fromPMC Specialties Group, Cincinnati, OH) 1,2-hexanediol (%) 1.0 1.0 1.01.0 1.0 1.0 1.0 Butyl oxitol glycol 2.0 2.0 2.0 2.0 2.0 2.0 2.0 ether(%) Triethanolamine (%) 0.2 0.2 0.2 0.2 0.2 0.2 0.2 Example 3 Dispersion(%) 25.8 25.8 25.8 25.5 24.2 26.8 24.7 IPA - Anhydrous (%) 2.0 2.0 2.02.0 2.0 2.0 2.0

The ink compositions described in the table above were formulated usinga two vessel method. A first vessel was used to make the ink base ordiluent. A second vessel was used to slowly dilute the pigmenteddispersion during a process commonly called a “letdown.” The equipmentused in the method of making the ink was glass.

First, the appropriate amount of water was added to the first vessel. Amixing device was then placed inside the vessel to agitate the water andprovide mixing while the other ingredients are added. Mixing wasachieved by using a magnetic stirring device. Next, the appropriateamounts of 2-pyrrolidone, PEG 400, 1,2-hexanediol, and butyl oxitolglycol ether were added to the vessel. These were allowed to dissolve.Then, the appropriate amount of triethanolamine was added and allowed todissolve. Finally, the appropriate amounts of Cobratec solution andBioban were added and allowed to dissolve.

The second vessel was prepared by adding the appropriate amount of thepigment dispersion made according to Example 3 to the vessel. A magneticstirring device was then placed into the vessel. After all of theingredients in the diluent had dissolved, the dispersion and the diluentwere mixed together. After the diluent and dispersion were combined, theink was mixed for about 1 hour, or until it was homogenous. Aftermixing, the ink was filtered using a 1 micron glass filter (availablefrom Whatman, Kent, England).

The print performance characteristics of the above inks on Xerox 4200paper are given below.

TABLE 17 Water Resistance. Visual Optical Density Ink # Salt Form ShiftB MEA 0.11 C K⁺ 0.12 D NH4⁺ 0.12 E TMA 0.10 F TEA 0.08 G Li⁺ 0.13 H Na⁺0.14

TABLE 18 Highlighter Resistance. Visual Optical Density Ink # Salt FormShift B MEA 0.00 C K⁺ 0.01 D NH4⁺ 0.01 E TMA 0.00 F TEA 0.00 G Li⁺ 0.00H Na⁺ 0.00

TABLE 19 Rub Resistance. Visual Optical Density Visual Optical DensityInk # Salt Form Before After B MEA 1.22 1.19 C K⁺ 1.26 1.22 D NH4⁺ 1.251.22 E TMA 1.21 1.18 F TEA 1.19 1.16 G Li⁺ 1.25 1.22 H Na⁺ 1.25 1.21

TABLE 20 ImageXpert Instrument Procedure 1.0 [Edge Acuity]. Ink # SaltForm Edge Acuity (microns) B MEA 20 C K⁺ 19 D NH4⁺ 17 E TMA 18 F TEA 16G Li⁺ 18 H Na⁺ 17

Example 27

Ink formulations comprising the color pigment dispersions preparedaccording to Examples 13 (Ink I) and 16 (Ink J) are given below:

TABLE 21 Inks I and J formulations. Ink Ink I J Water, deionized (%)41.3 41.3 Glycerine 14.0 14.0 PEG 600 2.0 2.0 Butyl carbitol 3.0 3.0Triethanolamine 0.1 0.1 33% Cobratec solution 0.3 0.3 Xbinx 19G 0.3 0.3Ethanol 2.0 2.0 Butanol 1.0 1.0 Example 13 Dispersion 36 0 Example 16Dispersion 0 36

The ink compositions described in the table above were formulated usinga two vessel method. A first vessel was used to make the ink base ordiluent. A second vessel was used to slowly dilute the pigmenteddispersion during a process commonly called a “letdown.” The equipmentused in the method of making the ink was glass.

First, water was added to the first vessel. A mixing device was thenplaced inside the vessel to agitate the water and provide mixing whilethe other ingredients are added. Mixing was achieved by using a magneticstirring device. Next, glycerine, PEG 600, butyl carbitol, ethanol, andbutanol were added to the vessel. These were allowed to dissolve. Then,triethanolamine was added and allowed to dissolve. Finally, Cobratecsolution and Xbinx 19G were added and allowed to dissolve.

The second vessel was prepared by adding the pigment dispersion madeaccording to Example 13 or Example 16 to the vessel. A magnetic stirringdevice was then placed into the vessel. After all of the ingredients inthe diluent had dissolved, the dispersion and the diluent were mixedtogether. After the diluent and dispersion were combined, the ink wasmixed for about 1 hour, or until it was homogenous. After mixing, theink was filtered using a 1 micron glass filter (available from Whatman,Kent, England).

The print performance characteristics of these inks on HP Multipurposepaper are provided below.

TABLE 22 Water Resistance. Visual Optical Density Ink Color Shift Ink IMagenta 0.11 Ink J Cyan 0.12

TABLE 23 Highlighter Smear. Visual Optical Density Ink Color Shift Ink IMagenta 0.00 Ink J Cyan 0.01

TABLE 24 Rub Resistance. Visual Optical Density Visual Optical DensityInk Color Before After Ink I Magenta 1.22 1.19 Ink J Cyan 1.26 1.22

TABLE 25 ImageXpert Instrument Procedure 1.0 [Edge Acuity]. Ink ColorEdge Acuity (microns) Ink I Magenta 39 Ink J Cyan 13

Example 28

The following ink formulation was made as described below andincorporated the self-dispersing pigment made according to Example 16.

TABLE 26 Ink K formulation. Ingredients % by Weight Water 41.3 Glycerine14 PEG 600 2 Butyl Carbitol 3 TEA 0.1 Cobratec 0.3 Xbinx 19G 0.3 Ethanol2 Butanol 1 Example 16 36 Dispersion

The ink composition described in the table above was formulated using atwo vessel method. A first vessel was used to make the ink base ordiluent. A second vessel was used to slowly dilute the pigmenteddispersion during a process commonly called a “letdown.” The equipmentused in the method of making the ink was glass.

First, water was added to the first vessel. A mixing device was thenplaced inside the vessel to agitate the water and provide mixing whilethe other ingredients are added. Mixing was achieved by using a magneticstirring device. Next, glycerine, PEG 600, butyl carbitol, ethanol, andbutanol were added to the vessel. These were allowed to dissolve. Then,triethanolamine was added and allowed to dissolve. Finally, Cobratecsolution and Xbinx 19G were added and allowed to dissolve.

The second vessel was prepared by adding the pigment dispersion madeaccording to Example 16 to the vessel. A magnetic stirring device wasthen placed into the vessel. After all of the ingredients in the diluenthad dissolved, the dispersion and the diluent were mixed together. Afterthe diluent and dispersion were combined, the ink was mixed for about 1hour, or until it was homogenous. After mixing, the ink was filteredusing a 1 micron glass filter (available from Whatman, Kent, England).

The print performance characteristics of this ink on HP Multipurposepaper are identified below.

TABLE 27 Print Performance Characteristics of Ink K. L 71.31 a* −18.82 b* −16.37  Line Width 236 microns Edge Acuity 13 microns Uniformity 3.4Horizontal Bleed −4 microns Vertical Bleed −2 microns

Example 29

The following ink formulation was made according to Example 28 andincorporated the self-dispersing pigment made according to Example 13.

TABLE 28 Ink L formulation. Ingredients % by Weight Water 41.3 Glycerine14 PEG 600 2 Butyl Carbitol 3 TEA 0.1 Cobratec 0.3 Xbinx 19G 0.3 Ethanol2 Butanol 1 Example 13 36 Dispersion

The print performance characteristics of this ink on HP Multipurposepaper are identified below.

TABLE 29 Print Performance Characteristics of Ink L. L 68.88 a* 27.26 b*−11.96  Line Width 198 microns Edge Acuity 39 microns Uniformity  4.69Horizontal Bleed 3 microns Vertical Bleed 1 microns

Example 30

The following ink formulation was made according to the proceduredescribed below and incorporated the self-dispersing pigment madeaccording to Example 10.

TABLE 30 Ink M formulation. Ingredients % by Weight Water, deionized 7.3Glycerine 99.7%, USP/EP, 14.0 OPTIM PEG600 Carb. Polyethlene Glycol 2.0Glycol Ether DB 3.0 Triethanolamine 85 0.1 Nipacide BIT 20 0.3(available from Clariant, Coventry, RI) Cobratec Solution 0.3IPA-Anhydrous 2.0 N-Butanol Eastman 1.0 Example 10 Dispersion 70.0

The ink composition described in the table above was formulated using atwo vessel method. A first vessel was used to make the ink base ordiluent. A second vessel was used to slowly dilute the pigmenteddispersion during a process commonly called a “letdown.” The equipmentused in the method of making the ink was glass.

First, water was added to the first vessel. A mixing device was thenplaced inside the vessel to agitate the water and provide mixing whilethe other ingredients are added. Mixing was achieved by using a magneticstirring device. Next, glycerine, PEG 600, glycol either DB, IPAanhydrous, and N-Butanol Eastman were added to the vessel. These wereallowed to dissolve. Then, triethanolamine 85 was added and allowed todissolve. Finally, Cobratec solution and Nipacide BIT 20 were added andallowed to dissolve.

The second vessel was prepared by adding the pigment dispersion madeaccording to Example 10 to the vessel. A magnetic stirring device wasthen placed into the vessel. After all of the ingredients in the diluenthad dissolved, the dispersion and the diluent were mixed together. Afterthe diluent and dispersion were combined, the ink was mixed for about 1hour, or until it was homogenous. After mixing, the ink was filteredusing a 1 micron glass filter (available from Whatman, Kent, England).

The physical parameters of this ink are identified below.

TABLE 31 Physical Parameters of Ink M. Viscosity (cps) 5.0 pH 8.4Conductivity (μOhms) 910.0 Surface Tension (dynes/cm) 40.7

The print performance characteristics of this ink are identified below.

TABLE 32 Print Performance Characteristics of Ink M. Epson Premium Xerox4200 Photo Paper L 67.71 72.01 a* 25.90 24.46 b* −17.05 −19.40 ΔE 22.429.9 Optical Density 0.52 0.45 Rub Resistance (OD 0.026 0.135Difference) Highlighter Resistance 0.008 0.045 (OD Difference) Waterresistance (OD 0.007 0.008 Difference) Mottle 6.1 2.1 Edge Acuity  47microns  8 microns Inter-Color Bleed −12 microns 15 microns Lightresistance 7.8 5.5

Example 31

The following ink formulation was made according to the proceduredescribed below and incorporated the self-dispersing pigment madeaccording to Example 7.

TABLE 33 Ink N formulation. Ingredients % by Weight Water, deionized58.4 2-Pyrrolidone water blend 5.3 PEG 600 Carb. Polyethylene Glycol13.0 Nipacide BIT 20 0.3 Triethanolamine 85 0.1 IPA-Anhydrous 2.0Example 7 Dispersion 21.0

The ink composition described in the table above was formulated using atwo vessel method. A first vessel was used to make the ink base ordiluent. A second vessel was used to slowly dilute the pigmenteddispersion during a process commonly called a “letdown.” The equipmentused in the method of making the ink was glass.

First, water was added to the first vessel. A mixing device was thenplaced inside the vessel to agitate the water and provide mixing whilethe other ingredients are added. Mixing was achieved by using a magneticstirring device. Next, 2-pyrrolidone, PEG 600, and IPA anhydrous wereadded to the vessel. These were allowed to dissolve. Then,triethanolamine 85 was added and allowed to dissolve. Finally, NipacideBIT 20 was added and allowed to dissolve.

The second vessel was prepared by adding the pigment dispersion madeaccording to Example 7 to the vessel. A magnetic stirring device wasthen placed into the vessel. After all of the ingredients in the diluenthad dissolved, the dispersion and the diluent were mixed together. Afterthe diluent and dispersion were combined, the ink was mixed for about 1hour, or until it was homogenous. After mixing, the ink was filteredusing a 1 micron glass filter (available from Whatman, Kent, England).

The physical parameters of this ink are identified below.

TABLE 34 Physical Parameters of Ink N. 1 Week at 70° C. 23 Days at 70°C. Stress Cycles Relative Relative Relative Initial Change Change ValueChange Viscosity 2.41 2.46 1.02 2.38 0.99 2.25 0.93 pH 8.26 7.26 0.887.12 0.86 7.72 0.93 Conductivity (μS) 303.00 500.00 1.65 640.00 2.11413.00 1.36 Surface Tension 43.80 44.10 1.01 45.20 1.03 44.30 1.01(dynes/cm) Heat at 70° C. - 0.06 0.08 1.33 0.07 1.17 Particle Count (#large particles >0.5 μm/mL E8) 3 0.06 0.04 0.67 Freeze/Thaw/HeatCycles - Freezer (8 H) to Countertop (8H) to Oven at 70° C. - ParticleCount (# large particles > 0.5 0.5 μm/mL E8)

The print performance characteristics of this ink are identified below.

TABLE 35 Print Performance Characteristics of Ink N. HP Multi- purposeOffice Depot Hammerill ColorLok Xerox 4200 104 Great White OpticalDensity 1.55 1.47 1.21 1.37 Rub Resistance 0.17 0.13 0.08 0.10 (ODDifference) Highlighter 0.07 0.02 0.01 0.01 Resistance (OD Difference)Water 0.11 0.10 0.05 0.06 resistance (OD Difference) Cartridge Start-Pass Pass Pass Pass up Line Width 268 284 276 288 Edge Acuity 9 12 13 15Mottle 0.690 0.980 1.500 1.560 Black Yellow 24 0 4 0 Bleed - HorizontalBlack Yellow 32 0 6 6 Bleed - Vertical

Example 32

The following ink formulation was made according to the proceduredescribed below and incorporated the self-dispersing pigment madeaccording to Example 7.

TABLE 36 Ink O formulation. Ingredients % by Weight Water, deionized58.6 2-Pyrrolidone water blend 10.0 1,5-pentanediol 5.0 PEG 600 Carb.Polyethylene Glycol 4.0 Nipacide BIT 20 0.3 Surfynol 104E solution 0.11,2-hexanediol 1.0 Example 7 Dispersion 21.0

The ink composition described in the table above was formulated using atwo vessel method. A first vessel was used to make the ink base ordiluent. A second vessel was used to slowly dilute the pigmenteddispersion during a process commonly called a “letdown.” The equipmentused in the method of making the ink was glass.

First, water was added to the first vessel. A mixing device was thenplaced inside the vessel to agitate the water and provide mixing whilethe other ingredients are added. Mixing was achieved by using a magneticstirring device. Next, 2-pyrrolidone, 1,5-pentanediol, PEG 600, and1,2-hexanediol were added to the vessel. These were allowed to dissolve.Then, Surfynol 104E solution and Nipacide BIT 20 were added and allowedto dissolve.

The second vessel was prepared by adding the pigment dispersion madeaccording to Example 7 to the vessel. A magnetic stirring device wasthen placed into the vessel. After all of the ingredients in the diluenthad dissolved, the dispersion and the diluent were mixed together. Afterthe diluent and dispersion were combined, the ink was mixed for about 1hour, or until it was homogenous. After mixing, the ink was filteredusing a 1 micron glass filter (available from Whatman, Kent, England).

The physical parameters of this ink are identified below.

TABLE 37 Physical Parameters of Ink O. 1 Week at 70° C. 23 Days at 70°C. Stress Cycles Relative Relative Relative Initial Change Change ValueChange Viscosity 2.95 2.98 1.01 2.87 0.97 2.77 0.94 pH 8.58 7.84 0.917.43 0.87 8.11 0.95 Conductivity (μS) 356.00 560.00 1.57 730.00 2.05477.00 1.34 Surface Tension 57.10 57.00 1.00 57.20 1.00 56.90 1.00(dynes/cm) Heat at 70° C. - 0.06 0.07 1.17 0.10 1.67 Particle Count (#large particles > 0.5 μm/mL E8) 3 0.06 0.12 2.00 Freeze/Thaw/HeatCycles - Freezer (8 H) to Countertop (8H) to Oven at 70° C. - ParticleCount (# large particles > 0.5 0.5 μm/mL E8)

The print performance characteristics of this ink are identified below.

TABLE 38 Print Performance Characteristics of Ink O. HP Multi- purposeOffice Depot Hammerill ColorLok Xerox 4200 104 Great White OpticalDensity 1.59 1.57 1.42 1.54 Rub Resistance 0.21 0.19 0.12 0.19 (ODDifference) Highlighter 0.14 0.06 0.02 0.07 Resistance (OD Difference)Water 0.15 0.19 0.07 0.14 resistance (OD Difference) Cartridge Start-Pass Pass Pass Pass up Line Width 244 267 257 269 Edge Acuity 8 11 11 15Mottle 0.680 0.670 1.410 0.840 Black Yellow 7 0 2 0 Bleed - HorizontalBlack Yellow 47 31 51 19 Bleed - Vertical

Thus, the invention provides, among other things, surface modifiedpigments and inks and methods of making and using the same. Variousfeatures and advantages of the invention are set forth in the followingclaims.

1. An ink composition comprising: a self-dispersing pigment comprisingabout 0.02 to about 1.0 mMoles of S and about 0.2 to about 2.0 mMoles ofactive hydrogen per gram of pigment; water; and an organic solvent. 2.The ink composition of claim 1, having a water resistance value of about0.00 to about 2.00.
 3. The ink composition of claim 1, having an edgeacuity value of about 0 microns to about 50 microns.
 4. The inkcomposition of claim 1, wherein the ink is a black ink having ahighlighter resistance of about 0 to about 2.00.
 5. The ink compositionof claim 1, wherein the ink is a color ink having a highlighterresistance of about 0 to about 0.10.
 6. The ink composition of claim 1,having a rub resistance of about 0.00 to about 2.00.
 7. The inkcomposition of claim 1, having a bleed value of about 0 microns to about100 microns.
 8. The ink composition of claim 1, having a line width ofabout 200 microns to about 350 microns.
 9. The ink composition of claim1, having an optical density of about 1.00 to about 3.00.
 10. The inkcomposition of claim 1, wherein the ink is a black ink having a mottleof about 0 to about 3.00.
 11. The ink composition of claim 1, whereinthe ink is a color ink having a mottle of about 0.00 to about 6.00 12.The ink composition of claim 1, wherein the pigment comprises at leastone of carbon black, pigment red 122, pigment yellow 19, pigment yellow74, pigment yellow 97, pigment yellow 138, pigment yellow 155, pigmentblue 15:1, pigment blue 15:3, solvent yellow 33, solvent blue 67, andcombinations thereof.
 13. The ink composition of claim 1, wherein thepigment comprises carbon black.
 14. The ink composition of claim 1,wherein the water soluble organic solvent comprises at least one ofwater, glycerine, diethylene glycol, polyethylene glycol, glycol ether,isopropanol, n-butyl alcohol, diethylene glycol butyl ether, butyloxitol glycol ether, ethanol, butanol, 2-pyrrolidone, 1,5-pentanediol,1,2-hexanediol, and a combination thereof.
 15. The ink composition ofclaim 1, wherein the water soluble organic solvent comprises about 1 toabout 40% of the ink composition.
 16. The ink composition of claim 1,further comprising a penetrant chosen from at least one of alkylalcohols having 1 to 4 carbon atoms, ethanol, methanol, n-butanol,sec-butyl alcohol, propanol, isopropanol, n-pentanol, diacetone alcohol,diols, 1,2-alkyl diols, diethylene glycol butyl ether, butyl oxitolglycol, 1,5-pentanediol, 1,2-hexanediol, ethylene glycol monomethylether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether,ethylene glycol monomethyl ether acetate, diethylene glycol monomethylether, diethylene glycol monoethyl ether, diethylene glycolmono-n-propyl ether, ethylene glycol mono-iso-propyl ether, diethyleneglycol mono-iso-propyl ether, ethylene glycol mono-n-butyl ether,ethylene glycol-mono-t-butyl ether, diethylene glycol mono-t-butylether, 1-methyl-1-methoxy butanol, propylene glycol monomethyl ether,propylene glycol monoethyl ether, propylene glycol mono-t-butyl ether,propylene glycol mono-n-propyl ether, propylene glycol mono-iso-propylether, dipropylene glycol monomethyl ether, dipropylene glycol monoethylether, dipropylene glycol mono-n-propyl ether, dipropylene glycolmono-iso-propyl ether, formamide; acetamide; dimethylsulfoxide;sorbitol; sorbitan; acetin; diacetin; triacetin; and sulfolane.
 17. Theink composition of claim 1, further comprising a pH modifier chosen fromat least one of an alkali hydroxide, an alkali carbonate, an alkalibicarbonate, ammonium hydroxide, potassium hydrogenphthalate, potassiumdihydrogenphosphate, sodium dihydrogenphosphate, sodium tetraborate,potassium hydrogentartrate, sodium hydrogencarbonate,tris(hydroxymethyl)aminomethane, tris(hydroxymethyl)aminomethanehydrochloride, triethylamine, dimethylethanolamine, triethanolamine, amineral acid, hydrochloric acid, sulfuric acid, and a combinationthereof.
 18. The ink composition of claim 1, further comprising abiocide chose from at least one of sodium benzoate, pentachlorophenolsodium, 2-pyridinethiol-1-oxide sodium, sodium sorbate, sodiumdehydroacetate, benz-isothiazolin-one, 1,2-dibenzothiazolin-3-one,methyl-isothiazolin-one, chloro-methyl-isothiazolin-one, and acombination thereof.
 19. The ink composition of claim 1, furthercomprising a nonionic surfactant.
 20. The ink composition of claim 24,wherein the surfactant comprises an ethoxylated acetylenic glycolsurfactant.
 21. The ink composition of claim 1, further comprising acorrosion inhibitor chosen from at least one of acidic sulfite, sodiumthiosulfate, ammonium thioglycolate, diisopropyl ammonium nitrite,pentaerythritol tetranitrate, dicyclohexyl ammonium nitrite,benzotriazole, tolyltriazole, carboxybenzotriazole, sodiumtolyltriazole, and a combination thereof.
 22. The ink composition ofclaim 1, further comprising at least one of an additional colorant, anantioxidant, an ultraviolet absorber, a chelating agent, an electricconductivity adjuster, a viscosity modifier, an oxygen absorber, ananti-kogation agent, an anti-curling agent, an anti-bleed agent, adefoamer, a buffer, and a combination thereof.
 23. A method of making anink composition comprising sulfonating a pigment; subsequently oxidizingthe pigment to produce a modified pigment; and incorporating themodified pigment into an ink.
 24. The method of claim 23, wherein themodified pigment comprises about 0.02 to about 1.0 mMoles of S and about0.2 to about 2.0 mMoles of active hydrogen per gram of pigment.